Merge vala-tools into main vala package
We had a way too complicated subpackage setup, with vala related utilities
split between vala and vala-tools packages. This led to most vala using
packages having to BuildRequire both vala and vala-tools. This commit
simplifies this by moving everything together into a single vala package, with
the exception of vala-devel that contains headers for linking with libvala.