clang-format: Fix namespace end comments for namespaces with attributes and macros.

Fixes PR39247.

While here, also make C++20 `namespace A::inline B::inline C` nested
inline namespaced definitions work.

Before:
    #define DEPRECATE_WOOF [[deprecated("meow")]]

    namespace DEPRECATE_WOOF woof {
    void f() {}
    } // namespace DEPRECATE_WOOFwoof

    namespace [[deprecated("meow")]] woof {
      void f() {}
    } // namespace [[deprecated("meow")]]woof

    namespace woof::inline bark {
      void f() {}
    } // namespace woof::inlinebark

Now:
    #define DEPRECATE_WOOF [[deprecated("meow")]]

    namespace DEPRECATE_WOOF woof {
    void f() {}
    } // namespace woof

    namespace [[deprecated("meow")]] woof {
    void f() {}
    } // namespace woof

    namespace woof::inline bark {
    void f() {}
    } // namespace woof::inline bark

(In addition to the fixed namespace end comments, also note the correct
indent of the namespace contents.)

Differential Revision: https://reviews.llvm.org/D65125

llvm-svn: 366831