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

[Owen Pan via cfe-commits]

owenca 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?

Now I'm leaning toward keeping the existing (buggy) behavior of `None` and using the new `AllowShortType` to allow wrapping after short return types.

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