Remove ImportMap (#11234)

## Summary

This PR removes the `ImportMap` implementation and all its routing
through ruff.

The import map was added in https://github.com/astral-sh/ruff/pull/3243
but we then never ended up using it to do cross file analysis.

We are now working on adding multifile analysis to ruff, and revisit
import resolution as part of it.


```
hyperfine --warmup 10 --runs 20 --setup "./target/release/ruff clean" \
              "./target/release/ruff check crates/ruff_linter/resources/test/cpython -e -s --extend-select=I" \
              "./target/release/ruff-import check crates/ruff_linter/resources/test/cpython -e -s --extend-select=I" 
Benchmark 1: ./target/release/ruff check crates/ruff_linter/resources/test/cpython -e -s --extend-select=I
  Time (mean ± σ):      37.6 ms ±   0.9 ms    [User: 52.2 ms, System: 63.7 ms]
  Range (min … max):    35.8 ms …  39.8 ms    20 runs
 
Benchmark 2: ./target/release/ruff-import check crates/ruff_linter/resources/test/cpython -e -s --extend-select=I
  Time (mean ± σ):      36.0 ms ±   0.7 ms    [User: 50.3 ms, System: 58.4 ms]
  Range (min … max):    34.5 ms …  37.6 ms    20 runs
 
Summary
  ./target/release/ruff-import check crates/ruff_linter/resources/test/cpython -e -s --extend-select=I ran
    1.04 ± 0.03 times faster than ./target/release/ruff check crates/ruff_linter/resources/test/cpython -e -s --extend-select=I
```

I suspect that the performance improvement should even be more
significant for users that otherwise don't have any diagnostics.


```
hyperfine --warmup 10 --runs 20 --setup "cd ../ecosystem/airflow && ../../ruff/target/release/ruff clean" \
              "./target/release/ruff check ../ecosystem/airflow -e -s --extend-select=I" \
              "./target/release/ruff-import check ../ecosystem/airflow -e -s --extend-select=I" 
Benchmark 1: ./target/release/ruff check ../ecosystem/airflow -e -s --extend-select=I
  Time (mean ± σ):      53.7 ms ±   1.8 ms    [User: 68.4 ms, System: 63.0 ms]
  Range (min … max):    51.1 ms …  58.7 ms    20 runs
 
Benchmark 2: ./target/release/ruff-import check ../ecosystem/airflow -e -s --extend-select=I
  Time (mean ± σ):      50.8 ms ±   1.4 ms    [User: 50.7 ms, System: 60.9 ms]
  Range (min … max):    48.5 ms …  55.3 ms    20 runs
 
Summary
  ./target/release/ruff-import check ../ecosystem/airflow -e -s --extend-select=I ran
    1.06 ± 0.05 times faster than ./target/release/ruff check ../ecosystem/airflow -e -s --extend-select=I

```

## Test Plan

`cargo test`

crates/ruff_linter/src/linter.rs

@@ -10,7 +10,6 @@ use rustc_hash::FxHashMap;
 
 use ruff_diagnostics::Diagnostic;
 use ruff_notebook::Notebook;
-use ruff_python_ast::imports::ImportMap;
 use ruff_python_ast::{PySourceType, Suite};
 use ruff_python_codegen::Stylist;
 use ruff_python_index::Indexer;
@@ -62,7 +61,7 @@ pub type FixTable = FxHashMap<Rule, usize>;
 
 pub struct FixerResult<'a> {
     /// The result returned by the linter, after applying any fixes.
-    pub result: LinterResult<(Vec<Message>, Option<ImportMap>)>,
+    pub result: LinterResult<Vec<Message>>,
     /// The resulting source code, after applying any fixes.
     pub transformed: Cow<'a, SourceKind>,
     /// The number of fixes applied for each [`Rule`].
@@ -84,10 +83,9 @@ pub fn check_path(
     source_kind: &SourceKind,
     source_type: PySourceType,
     tokens: TokenSource,
-) -> LinterResult<(Vec<Diagnostic>, Option<ImportMap>)> {
+) -> LinterResult<Vec<Diagnostic>> {
     // Aggregate all diagnostics.
     let mut diagnostics = vec![];
-    let mut imports = None;
     let mut error = None;
 
     // Collect doc lines. This requires a rare mix of tokens (for comments) and AST
@@ -169,19 +167,18 @@ pub fn check_path(
                     ));
                 }
                 if use_imports {
-                    let (import_diagnostics, module_imports) = check_imports(
+                    let import_diagnostics = check_imports(
                         &python_ast,
                         locator,
                         indexer,
                         &directives.isort,
                         settings,
                         stylist,
-                        path,
                         package,
                         source_type,
                         cell_offsets,
                     );
-                    imports = module_imports;
+
                     diagnostics.extend(import_diagnostics);
                 }
                 if use_doc_lines {
@@ -340,7 +337,7 @@ pub fn check_path(
         }
     }
 
-    LinterResult::new((diagnostics, imports), error)
+    LinterResult::new(diagnostics, error)
 }
 
 const MAX_ITERATIONS: usize = 100;
@@ -410,7 +407,7 @@ pub fn add_noqa_to_path(
     // TODO(dhruvmanila): Add support for Jupyter Notebooks
     add_noqa(
         path,
-        &diagnostics.0,
+        &diagnostics,
         &locator,
         indexer.comment_ranges(),
         &settings.external,
@@ -429,7 +426,7 @@ pub fn lint_only(
     source_kind: &SourceKind,
     source_type: PySourceType,
     data: ParseSource,
-) -> LinterResult<(Vec<Message>, Option<ImportMap>)> {
+) -> LinterResult<Vec<Message>> {
     // Tokenize once.
     let tokens = data.into_token_source(source_kind, source_type);
 
@@ -465,12 +462,7 @@ pub fn lint_only(
         tokens,
     );
 
-    result.map(|(diagnostics, imports)| {
-        (
-            diagnostics_to_messages(diagnostics, path, &locator, &directives),
-            imports,
-        )
-    })
+    result.map(|diagnostics| diagnostics_to_messages(diagnostics, path, &locator, &directives))
 }
 
 /// Convert from diagnostics to messages.
@@ -583,7 +575,7 @@ pub fn lint_fix<'a>(
             code: fixed_contents,
             fixes: applied,
             source_map,
-        }) = fix_file(&result.data.0, &locator, unsafe_fixes)
+        }) = fix_file(&result.data, &locator, unsafe_fixes)
         {
             if iterations < MAX_ITERATIONS {
                 // Count the number of fixed errors.
@@ -600,15 +592,12 @@ pub fn lint_fix<'a>(
                 continue;
             }
 
-            report_failed_to_converge_error(path, transformed.source_code(), &result.data.0);
+            report_failed_to_converge_error(path, transformed.source_code(), &result.data);
         }
 
         return Ok(FixerResult {
-            result: result.map(|(diagnostics, imports)| {
-                (
-                    diagnostics_to_messages(diagnostics, path, &locator, &directives),
-                    imports,
-                )
+            result: result.map(|diagnostics| {
+                diagnostics_to_messages(diagnostics, path, &locator, &directives)
             }),
             transformed,
             fixed,