Fix rhbz #2248872
Ensure the versioned llvm-config alternative gets removed during major
upgrades of the non-compat package.
Also add code that removes the versioned llvm-config alternatives of
the previous 3 LLVM versions. These versions didn't remove their own
versioned llvm-config alternative, leading to broken output, e.g.
llvm-config-16 points to llvm-config-64 from LLVM 17.