[clang] [llvm] [Clang] Update Unicode version to 15.1 (PR #77147)

[via llvm-commits]

cor3ntin wrote:

@MaskRay sadly, At the moment we have no automation whatsoever for some of the tables (only character names and case folding have upstream scripts). We really should write a script to generate the tables. (the one i use is fairly nasty and i need to copy each table in the corresponding file manually, it's... not great)

https://github.com/llvm/llvm-project/pull/77147