[clang] [clang-format] Add BreakAfterReturnType option to deprecate AlwaysBreakAfterReturnType. (PR #80827)

[Owen Pan via cfe-commits]

owenca wrote:

@rmarker we only need to change the user-facing part and should leave the internal naming unchanged (at least in this patch) in order to have the smallest diff possible. I've added the support for deprecating/renaming top-level struct-type options to `dump_format_style.py` in #81093.

https://github.com/llvm/llvm-project/pull/80827