prepared-metadata: harden concurrent cache safety #1377

Job	Run time
Test wheels building / Build source distribution	9s
Test wheels building / Prepare matrix to run for 3.13 on `linux,macos-x86,macos-arm,windows,linux-aarch64`	3s
Test wheels building / Build wheels for macos-x86 on macos-15-intel	31m 44s
Test wheels building / Build wheels for linux on ubuntu-24.04	21m 50s
Test wheels building / Build wheels for linux-aarch64 on ubuntu-24.04-arm	16m 54s
Test wheels building / Build wheels for macos-arm on macos-14	11m 3s
Test wheels building / Build wheels for windows on windows-2022	23m 16s
	1h 44m 59s

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