[feat] Make sys::windows::os_str::Slice repr(transparent)

[gimbling-away]

Fixes #96577

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[ChrisDenton]

Looks ok to me. The sys modules are private so this shouldn't affect the public API. But if you did want to fix the error in your first commit then you could try adding pub(crate) to both Buf and Slice.

[thomcc]

Seems fine.

@bors r+

[bors]

📌 Commit 3b5fe26 has been approved by thomcc

[bors]

⌛ Testing commit 3b5fe26 with merge db5b365...

[bors]

☀️ Test successful - checks-actions
Approved by: thomcc
Pushing db5b365 to master...

[rust-timer]

Finished benchmarking commit (db5b365): comparison url.

Summary: This benchmark run did not return any relevant results.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression