[clang] [clang-format]: Add `Custom` to `ShortFunctionStyle`; add new AllowShortFunctionsOnASingleLineOptions for granular setup (PR #134337)

[Owen Pan via cfe-commits]

================
@@ -5685,11 +5685,9 @@ bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
     if (Right.is(tok::r_brace) && Left.is(tok::l_brace) &&
         !Left.Children.empty()) {
       // Support AllowShortFunctionsOnASingleLine for JavaScript.
-      return Style.AllowShortFunctionsOnASingleLine == FormatStyle::SFS_None ||
-             Style.AllowShortFunctionsOnASingleLine == FormatStyle::SFS_Empty ||
-             (Left.NestingLevel == 0 && Line.Level == 0 &&
-              Style.AllowShortFunctionsOnASingleLine &
-                  FormatStyle::SFS_InlineOnly);
+      return !(Left.NestingLevel == 0 && Line.Level == 0
+                   ? Style.AllowShortFunctionsOnASingleLine.isAll()
----------------
owenca wrote:

Looks like this is even worse than what @sstwcw suggested because it also seems incorrect if the following is true:
```
Left.NestingLevel == 0 && Line.Level == 0 && Other && !Inline
```

https://github.com/llvm/llvm-project/pull/134337