This PR bundles together a few commits that improve how the Action handles what CLI version is being used. In particular:

1. We can cache the result of codeql version to avoid spawning the process many times. This will be important since the later changes will result in us using the version much more frequently.
2. A few flags that are only available in recent CodeQL CLIs are moved to be behind a version check, so we can be compatible with older versions. @henrymercer I'd be very keen to have your eyes on this commit to let me know if you foresee any issues with not passing those flags (we don't need full functionality, but we shouldn't break either).
3. The Action now checks that the CodeQL version is above a constant of CODEQL_MINIMUM_VERSION that records the oldest version we support. This is currently set to 2.3.1 when some breaking changes to how the tracing environment is configured occurred.
4. The PR checks now also test against the oldest supported version in addition to the version in the toolcache, the latest release, and the latest nightly build.

I think the integration tests workflow is in need of some refactoring now that I have added this additional complexity to it, but I propose delaying this to a later PR.