chore(ci, mongodb-runner): cache mongodb download on windows COMPASS-10932

[Anemy]

Only uses them for a week so we avoid getting stale ones. Github automatically cleans up unused cache items. This does mean once a week CI will be that slower run.

[Anemy]

Maybe we want to avoid using env here and instead pass the downloadDir everywhere? It will add a bit more code and could lead to folks not passing it though.

[nbbeeken]

I feel like env is fine but since this is in the CLI could we add it to the help menu along side the --downloadDir flag and call this PR a feat -> (feat to add env var control for the download location)

[Copilot]

Pull request overview

This PR aims to speed up Windows CI runs by caching downloaded MongoDB server binaries between workflow executions, wiring the cache location into mongodb-runner via a new environment-variable default.

Changes:

• mongodb-runner: prefer MONGODB_RUNNER_DOWNLOAD_DIR (when set) as the download directory before falling back to tmpDir.
• CI: add a Windows-only cache for MongoDB binaries with weekly rotation and set MONGODB_RUNNER_DOWNLOAD_DIR accordingly.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/mongodb-runner/src/mongocluster.ts	Uses MONGODB_RUNNER_DOWNLOAD_DIR as a default download location for MongoDB binaries.
.github/workflows/check-test.yaml	Adds Windows-only cache + weekly rotation key and exports download dir env var for tests.

Suppressed comments (1)

.github/workflows/check-test.yaml:129

• $GITHUB_ENV should be quoted to avoid failures if the runner path contains spaces or special characters.

        run: echo "MONGODB_RUNNER_DOWNLOAD_DIR=${RUNNER_TEMP}/mongodb-binaries" >> $GITHUB_ENV

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