[clang] [polly] [clang-format] Add AllowShortType option for AlwaysBreakAfterReturnType. (PR #78011)

[Björn Schäpers via cfe-commits]

HazardyKnusperkeks wrote:

> @mydeveloperday @HazardyKnusperkeks @rymiel this patch fixes a very old bug and will cause behavior changes whether the default is changed to the new `AllowShortType` or left at `None`. Which way should we go?

What would change if the default was kept at `None`? I don't see it.

https://github.com/llvm/llvm-project/pull/78011