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.
Eventually these files will subsume the current `queries.xml` files
at the top of query-containing and library directories. For now they're
just here to support internal testing of the tooling support for them
we're writing on.
Format and contents is a work in progress. If you're not in Semmle,
don't depend on anything here making sense (or staying stable) until
you see the version tags increase to something nonzero.