Treat type aliases as typing-only expressions (#7968)

## Summary

Given `type RecordOrThings = Record | int | str`, the right-hand side
won't be evaluated at runtime. Same goes for `Record` in `type
RecordCallback[R: Record] = Callable[[R], None]`. This PR modifies the
visitation logic to treat them as typing-only.

Closes https://github.com/astral-sh/ruff/issues/7966.

crates/ruff_linter/resources/test/fixtures/flake8_type_checking/TCH004_15.py

@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+from collections.abc import Callable
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from .foo import Record
+
+type RecordOrThings = Record | int | str
+type RecordCallback[R: Record] = Callable[[R], None]
+
+
+def process_record[R: Record](record: R) -> None:
+    ...
+
+
+class RecordContainer[R: Record]:
+    def add_record(self, record: R) -> None:
+        ...

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -580,7 +580,9 @@ where
                 if let Some(type_params) = type_params {
                     self.visit_type_params(type_params);
                 }
-                self.visit_expr(value);
+                // The value in a `type` alias has annotation semantics, in that it's never
+                // evaluated at runtime.
+                self.visit_annotation(value);
                 self.semantic.pop_scope();
                 self.visit_expr(name);
             }
@@ -1766,7 +1768,7 @@ impl<'a> Checker<'a> {
                     bound: Some(bound), ..
                 }) = type_param
                 {
-                    self.visit_expr(bound);
+                    self.visit_annotation(bound);
                 }
             }
         }

crates/ruff_linter/src/rules/flake8_type_checking/mod.rs

@@ -22,6 +22,7 @@ mod tests {
     #[test_case(Rule::RuntimeImportInTypeCheckingBlock, Path::new("TCH004_12.py"))]
     #[test_case(Rule::RuntimeImportInTypeCheckingBlock, Path::new("TCH004_13.py"))]
     #[test_case(Rule::RuntimeImportInTypeCheckingBlock, Path::new("TCH004_14.pyi"))]
+    #[test_case(Rule::RuntimeImportInTypeCheckingBlock, Path::new("TCH004_15.py"))]
     #[test_case(Rule::RuntimeImportInTypeCheckingBlock, Path::new("TCH004_2.py"))]
     #[test_case(Rule::RuntimeImportInTypeCheckingBlock, Path::new("TCH004_3.py"))]
     #[test_case(Rule::RuntimeImportInTypeCheckingBlock, Path::new("TCH004_4.py"))]

crates/ruff_linter/src/rules/flake8_type_checking/snapshots/ruff_linter__rules__flake8_type_checking__tests__runtime-import-in-type-checking-block_TCH004_15.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff_linter/src/rules/flake8_type_checking/mod.rs
+---
+