LLVM version 15

All LLVM sub-projects in Fedora have been updated to version 15, and there has been be a soname version change for the LLVM libraries. Compatibility packages clang14 and llvm14 are available to ensure that packages that currently depend on CLang and LLVM version 14 libraries will continue to work.

A full list of changes in LLVM 15 is available in the upstream LLVM Release Notes.