[FIX] Prevent rate limiting by changing setup.py to only reach out to the GitHub api to get the latest codeql cli version if args.check_latest_cli is set

[nickcopi]

Before this change, it would always call codeql.get_latest_codeql_github_version() and only check if it should actually do anything with it afterwards based on args.check_latest_cli. This meant that it was required to hit the github API to get the latest codeql version regardless of args.check_latest_cli being set, which could lead to API ratelimiting and the setup script crashing before it could launch codeql.

This change gates the codeql.get_latest_codeql_github_version() call behind a args.check_latest_cli to prevent unnecessary reliance on being able to reach the github API if the codeql latest version isn't going to be used because the check_latest_cli argument isn't set.

[travisgosselin]

I already had a fix for this in: #47 .... but had issues getting licensing approval for the commit until today. This also includes support for a GITHUB_TOKEN for an authorized check/download of the github data. Our changes look pretty much the same for the initial version check.