Fix Windows GNU staticlib output naming (#4231)

## Summary

Make Rust static-library naming ABI-aware on Windows.

Rust emits `lib<crate>.a` for the GNU and GNULLVM Windows ABIs, while
MSVC emits `<crate>.lib`. The generated Rust toolchain currently selects
`.lib` from the operating system alone, and `determine_lib_name` removes
the `lib` prefix for every Windows static library. As a result, Bazel
declares an output different from the file emitted by rustc for Windows
GNU-like targets.

This change passes the target ABI through repository and toolchain
generation, selects `.a` for Windows GNU/GNULLVM static libraries, and
preserves their `lib` prefix. MSVC behavior and Windows dynamic-library
naming remain unchanged.

Regression coverage exercises the extension mapping, rendered toolchain
metadata, final GNU/GNULLVM/MSVC static-library names, and the unchanged
GNU `cdylib` name.