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/options.rs

@@ -796,6 +796,16 @@ pub struct LintCommonOptions {
     )]
     pub typing_modules: Option<Vec<String>>,
 
+    /// A list of modules which is allowed even thought they are not used
+    /// in the code.
+    ///
+    /// This is useful when a module has a side effect when imported.
+    #[option(
+        default = r#"[]"#,
+        value_type = "list[str]",
+        example = r#"allowed-unused-imports = ["hvplot.pandas"]"#
+    )]
+    pub allowed_unused_imports: Option<Vec<String>>,
     /// A list of rule codes or prefixes to consider non-fixable.
     #[option(
         default = "[]",
@@ -2812,12 +2822,28 @@ pub struct PyflakesOptions {
         example = "extend-generics = [\"django.db.models.ForeignKey\"]"
     )]
     pub extend_generics: Option<Vec<String>>,
+
+    /// A list of modules to ignore when considering unused imports.
+    ///
+    /// Used to prevent violations for specific modules that are known to have side effects on
+    /// import (e.g., `hvplot.pandas`).
+    ///
+    /// Modules in this list are expected to be fully-qualified names (e.g., `hvplot.pandas`). Any
+    /// submodule of a given module will also be ignored (e.g., given `hvplot`, `hvplot.pandas`
+    /// will also be ignored).
+    #[option(
+        default = r#"[]"#,
+        value_type = "list[str]",
+        example = r#"allowed-unused-imports = ["hvplot.pandas"]"#
+    )]
+    pub allowed_unused_imports: Option<Vec<String>>,
 }
 
 impl PyflakesOptions {
     pub fn into_settings(self) -> pyflakes::settings::Settings {
         pyflakes::settings::Settings {
             extend_generics: self.extend_generics.unwrap_or_default(),
+            allowed_unused_imports: self.allowed_unused_imports.unwrap_or_default(),
         }
     }
 }