ci(windows): Introduce setup-dev-drive.ps1, maximize dev drive usage

[fasterthanlime]

As suggested by @samypr100 on #6680:
#6680 (comment)

Summary

Instead of using UV_INTERNAL__TEST_DIR, it simply exports TEMP when running Windows jobs.

Test Plan

I'm going to run this manually under ProcMon on my Windows machine and see where uv writes temp files, hopefully to the dev drive and not %(LOCAL)APPDATA% or something.

I'm going to commit a dummy code change and look at build time changes in CI.

[fasterthanlime]

So: in uv/tests/common, there's a bit of code that makes a directory under the data dir. There's a rationale for macOS.

We need to keep exporting the internal var for Windows, I'm afraid, but I think setting TEMP there is also a good idea (for other tools), and I've deduplicated the dev-drive setup into its own PowerShell script. Let's see if it still works.

[samypr100]

If there's any interest, I also maintain a separate https://github.com/samypr100/setup-dev-drive which could help achieve the same here if we want to cleanup and have more control on the settings per job

[samypr100]

Was UV_INTERNAL__TEST_DIR going to be removed as part of this PR? Maybe a testing remnant

[zanieb]

I think this is addressed in #6858 (comment)

[samypr100]

I see, thanks

[fasterthanlime]

it can't be (woops, zanieb got to this first)

#6858 (comment)