[bazel] Improve runfiles handling (#10098)

we can't use runfiles directory on Windows due to path lengths, so swap
to manifest strategy. Parsing the manifest is a bit complex and the
format is changing in Bazel upstream, so pull in the official Rust
library (via a small hack to make it importable...) and cleanup all the
associated logic to work cleanly in both bazel and cargo without extra
confusion

codex-rs/core/tests/suite/cli_stream.rs

@@ -16,7 +16,7 @@ use wiremock::matchers::path;
 
 fn repo_root() -> std::path::PathBuf {
     #[expect(clippy::expect_used)]
-    find_resource!(".").expect("failed to resolve repo root")
+    codex_utils_cargo_bin::repo_root().expect("failed to resolve repo root")
 }
 
 fn cli_responses_fixture() -> std::path::PathBuf {