Also remove `@frameSize`, closing #3654.
While the other machinery might remain depending on #23446, it is
settled that there will not be `async`/ `await` keywords in the
language.
Currently, the compiler (like @typeName) writes it `fn(...) Type` but
zig fmt writes it `fn (...) Type` (notice the space after `fn`).
This inconsistency is now resolved and function types are consistently
written the zig fmt way. Before this there were more `fn (...) Type`
occurrences than `fn(...) Type` already.
