GODRIVER-3313 Skip CSOT spec tests on Windows and macOS.

[matthewdale]

GODRIVER-3313

Summary

• Add logic to skip all CSOT spec and prose tests if the SKIP_CSOT_TESTS environment variable is set to "true".
• Set the SKIP_CSOT_TESTS=true environment variable on Windows and macOS CI tasks.

Background & Motivation

The timings are not as predictable on these platforms, leading to intermittent failures.

[mongodb-drivers-pr-bot]

API Change Report

No changes found!

[matthewdale]

drivers-pr-bot please backport to master

[mongodb-drivers-pr-bot]

Sorry, unable to cherry-pick to master, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout -b cherry-pick-master-8192e810e341abdae37b50e596c4f05b51992691 master

git fetch origin 8192e810e341abdae37b50e596c4f05b51992691

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 8192e810e341abdae37b50e596c4f05b51992691

3. You will likely have some merge/cherry-pick conflicts here, fix them and commit:

git commit -am {message}

4. Push to a named branch:

git push origin cherry-pick-master-8192e810e341abdae37b50e596c4f05b51992691

5. Create a PR against branch master. I would have named this PR:

"GODRIVER-3313 Skip CSOT spec tests on Windows and macOS. (#1818) [master]"