Add allow-unused-imports setting for unused-import rule (F401) (#13601)

## Summary
Resolves https://github.com/astral-sh/ruff/issues/9962 by allowing a
configuration setting `allowed-unused-imports`

TODO:
- [x] Figure out the correct name and place for the setting; currently,
I have added it top level.
- [x] The comparison is pretty naive. I tried using `glob::Pattern` but
couldn't get it to work in the configuration.
- [x] Add tests
- [x] Update documentations

## Test Plan

`cargo test`

crates/ruff_workspace/src/configuration.rs

@@ -626,6 +626,7 @@ pub struct LintConfiguration {
     pub logger_objects: Option<Vec<String>>,
     pub task_tags: Option<Vec<String>>,
     pub typing_modules: Option<Vec<String>>,
+    pub allowed_unused_imports: Option<Vec<String>>,
 
     // Plugins
     pub flake8_annotations: Option<Flake8AnnotationsOptions>,
@@ -738,6 +739,7 @@ impl LintConfiguration {
             task_tags: options.common.task_tags,
             logger_objects: options.common.logger_objects,
             typing_modules: options.common.typing_modules,
+            allowed_unused_imports: options.common.allowed_unused_imports,
             // Plugins
             flake8_annotations: options.common.flake8_annotations,
             flake8_bandit: options.common.flake8_bandit,
@@ -1106,6 +1108,9 @@ impl LintConfiguration {
                 .or(config.explicit_preview_rules),
             task_tags: self.task_tags.or(config.task_tags),
             typing_modules: self.typing_modules.or(config.typing_modules),
+            allowed_unused_imports: self
+                .allowed_unused_imports
+                .or(config.allowed_unused_imports),
             // Plugins
             flake8_annotations: self.flake8_annotations.combine(config.flake8_annotations),
             flake8_bandit: self.flake8_bandit.combine(config.flake8_bandit),
@@ -1327,6 +1332,7 @@ fn warn_about_deprecated_top_level_lint_options(
         explicit_preview_rules,
         task_tags,
         typing_modules,
+        allowed_unused_imports,
         unfixable,
         flake8_annotations,
         flake8_bandit,
@@ -1425,6 +1431,9 @@ fn warn_about_deprecated_top_level_lint_options(
     if typing_modules.is_some() {
         used_options.push("typing-modules");
     }
+    if allowed_unused_imports.is_some() {
+        used_options.push("allowed-unused-imports");
+    }
 
     if unfixable.is_some() {
         used_options.push("unfixable");