[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/utils/cargo-bin/repo_root.marker

@@ -0,0 +1 @@
+