Added allow-expect-in-tests / allow-unwrap-in-tests (#2328)

This PR:
* Added the clippy.toml to configure allowable expect / unwrap usage in
tests
* Removed as many expect/allow lines as possible from tests
* moved a bunch of allows to expects where possible

Note: in integration tests, non `#[test]` helper functions are not
covered by this so we had to leave a few lingering `expect(expect_used`
checks around

codex-rs/apply-patch/src/lib.rs

@@ -166,7 +166,7 @@ impl ApplyPatchAction {
             panic!("path must be absolute");
         }
 
-        #[allow(clippy::expect_used)]
+        #[expect(clippy::expect_used)]
         let filename = path
             .file_name()
             .expect("path should not be empty")
@@ -179,7 +179,7 @@ impl ApplyPatchAction {
 *** End Patch"#,
         );
         let changes = HashMap::from([(path.to_path_buf(), ApplyPatchFileChange::Add { content })]);
-        #[allow(clippy::expect_used)]
+        #[expect(clippy::expect_used)]
         Self {
             changes,
             cwd: path
@@ -682,8 +682,6 @@ pub fn print_summary(
 
 #[cfg(test)]
 mod tests {
-    #![allow(clippy::unwrap_used)]
-
     use super::*;
     use pretty_assertions::assert_eq;
     use std::fs;

codex-rs/apply-patch/src/parser.rs

@@ -427,7 +427,6 @@ fn parse_update_file_chunk(
 }
 
 #[test]
-#[allow(clippy::unwrap_used)]
 fn test_parse_patch() {
     assert_eq!(
         parse_patch_text("bad", ParseMode::Strict),