[red-knot] Expand test corpus (#14360)

## Summary

- Add 383 files from `crates/ruff_python_parser/resources` to the test
corpus
- Add 1296 files from `crates/ruff_linter/resources` to the test corpus
- Use in-memory file system for tests
- Improve test isolation by cleaning the test environment between checks
- Add a mechanism for "known failures". Mark ~80 files as known
failures.
- The corpus test is now a lot slower (6 seconds).

Note:
While `red_knot` as a command line tool can run over all of these
files without panicking, we still have a lot of test failures caused by
explicitly "pulling" all types.

## Test Plan

Run `cargo test -p red_knot_workspace` while making sure that
- Introducing code that is known to lead to a panic fails the test
- Removing code that is known to lead to a panic from
`KNOWN_FAILURES`-files also fails the test

crates/ruff_db/src/system/path.rs

@@ -491,6 +491,12 @@ impl From<&str> for SystemPathBuf {
     }
 }
 
+impl From<String> for SystemPathBuf {
+    fn from(value: String) -> Self {
+        SystemPathBuf::from_utf8_path_buf(Utf8PathBuf::from(value))
+    }
+}
+
 impl Default for SystemPathBuf {
     fn default() -> Self {
         Self::new()