This PR separates the core cpp packs into `codeql/cpp-queries` and
`codeql/cpp-all`.
There are very few lines of code changed. Almost all changes are moving
files around.
This will allow `codeql resolve tests --ignore-dubious-cases`
(and thus the VSCode extension) to recognize all `.ql` files in those
packs as test cases, even if they don't have accompanying `.expected`
files.
CLI versions prior to 2.1.0 will choke on this, but it's almost 10
months since that came out.
