[clang-format] Disallow requires clauses to become function declarations

There already exists logic to disallow requires *expressions* to be
treated as function declarations, but this expands it to include
requires *clauses*, when they happen to also be parenthesized.

Previously, in the following case:

```
template <typename T>
  requires(Foo<T>)
T foo();
```

The line with the requires clause was actually being considered as the
line with the function declaration due to the parentheses, and the
*real* function declaration on the next line became a trailing
annotation

(Together with https://reviews.llvm.org/D134049) Fixes https://github.com/llvm/llvm-project/issues/56213

Reviewed By: HazardyKnusperkeks, owenpan

Differential Revision: https://reviews.llvm.org/D134052