path/filepath: simplify chdir and error handling in tests

[aimuz]

This change simplifies the test code for changing directories by
utilizing t.TempDir() within chtmpdir function. It also replaces os.Exit(1)
with t.Fatalf to handle errors more consistently with Go's testing
practice.

The cleanup process is now managed with t.Cleanup, ensuring that any
created temporary directories are removed without the need for a
deferred restore function.

Updates #45182

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[gopherbot]

This PR (HEAD: 25ba510) has been imported to Gerrit for code review.

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[gopherbot]

Message from qiulaidongfeng:

Patch Set 2: Run-TryBot+1

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[gopherbot]

Message from Gopher Robot:

Patch Set 2:

(1 comment)

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[gopherbot]

Message from Gopher Robot:

Patch Set 2: TryBot-Result+1

(1 comment)

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[gopherbot]

This PR is being closed because golang.org/cl/546217 has been abandoned.

Obsoleted by CL 529896