[clang] clang-format: Add "AllowShortNamespacesOnASingleLine" option (PR #105597)

[Galen Elias via cfe-commits]

galenelias wrote:

> I don't think we want to add any tests whose formats are questionable or still under discussion. WDYT @mydeveloperday @HazardyKnusperkeks @rymiel ?

Ok, that's fair.  I have removed these tests.  Thanks for the detailed response and context.

https://github.com/llvm/llvm-project/pull/105597