[tools] Add apply_patch tool (#2303)

## Summary
We've been seeing a number of issues and reports with our synthetic
`apply_patch` tool, e.g. #802. Let's make this a real tool - in my
anecdotal testing, it's critical for GPT-OSS models, but I'd like to
make it the standard across GPT-5 and codex models as well.

## Testing
- [x] Tested locally
- [x] Integration test

codex-rs/exec/Cargo.toml

@@ -44,3 +44,5 @@ assert_cmd = "2"
 libc = "0.2"
 predicates = "3"
 tempfile = "3.13.0"
+wiremock = "0.6"
+core_test_support = { path = "../core/tests/common" }