tiny speedup in shutil fast copy on Windows

[landfillbaby]

can't see why the final write was doing a 2nd lookup of fdst.write

[the-knights-who-say-ni]

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[landfillbaby]

do i really need to sign the CLA for a single byte of changes? can't i just say it's WTFPL or something
edit: ok fine i did it

[landfillbaby]

yeah looking at the original PRs that added this stuff, #7160 and #7681, it seems like without the with statements there's no proper memoryview deallocation, and a CopyFile[Ex]W implementation was reverted due to those functions copying too much with no flag to disable it (metadata, forks, etc)

[landfillbaby]

i also just noticed it attempts a 2nd read after the case where output is less than the buffer size. unless that's intended i'm adding a break

[github-actions]

This PR is stale because it has been open for 30 days with no activity.