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

[Owen Pan via cfe-commits]

owenca wrote:

> Now that we've got both options, should we keep them? Currently, `None` sometimes forbids breaking after short return types and sometimes allows it and just bases things off the penalty configuration. I feel like there will be some people who use `None` who would want the behaviour to be consistent one way and the other group wanting it consistent the opposite. With both, they can decide for themselves. Especially since the implementation for both is pretty simple and self-contained.

+1. In addition, we should deprecate `None` (in documentation only) and rename `AllowShortType` to `Automatic`, followed by `ExceptShortType` which means "`Automatic` except for short return types". Then IMO `ExceptShortType` is unambiguous. If you still think `NeverShortType` is clearer, I would change it to `NotShortType`.

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