Ensure CodeQL Runner is up to date

[jhutchings1]

Since the CodeQL runner is distributed as a binary, there's a good chance that it could become out of date. We need to add functionality which outputs a message which warns users when the runner is too old.

We could optionally check this repo's releases using the API, but for on premises customers, that may not be an acceptable solution, so we'd need to make it configurable.