feat: Manually triggered window PoSt

[magik6k]

Related Issues

(probably exist)

Proposed Changes

Right now this PR adds an env var which will run window post compute after winning post warmup - this makes it possible to check that drivers are working correctly.

After #7600 lands, this will probably turn into a CLI command, maybe.

Blocked on #7600

Checklist

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[magik6k]

Needs to be rewritten to for PoSt workers