[clang] [clang-format]: Add `StaticInlineOnly` and `StaticInline` options to `ShortFunctionStyle` (PR #133598)

[Owen Pan via cfe-commits]

owenca wrote:

> @owenca, just to confirm - you are suggesting to add `Custom` string to `AllowShortFunctionsOnASingleLine` and new parameter (`AllowShortFunctionsOnASingleLineOptions` for example) which will control behavior if `AllowShortFunctionsOnASingleLine == Custom`?

Yep.

> What options should be present? I think we can start with `Inline`, `Empty`, `static inline`, `constexpr` (?).

Yes, but can you split it into two patches? The first would be NFC and only cover `Inline` and `Empty`.

https://github.com/llvm/llvm-project/pull/133598