[clang-format] Fix wrong indentation after trailing requires clause.

[curdeius]

Summary

Fixes https://github.com/llvm/llvm-project/issues/52834.

Before this patch, clang-format would wrongly parse top-level entities (e.g. namespaces) and format:

template<int I>
constexpr void foo requires(I == 42) {}
namespace ns {
void foo() {}
}  // namespace ns

into:

template<int I>
constexpr void foo requires(I == 42) {}
namespace ns {

void foo() {}

} // namespace ns

with configuration:

NamespaceIndentation: None

`

[HazardyKnusperkeks]

I really need to get my requires patch done...

clang/lib/Format/UnwrappedLineParser.cpp

case tok::at:
         break;
       }
       break;
     case tok::kw_concept:
       parseConcept();
       return;
     case tok::kw_requires:
       parseRequires();
-      break;
+      return;
     case tok::kw_enum:
       // Ignore if this is part of "template <enum ...".
       if (Previous && Previous->is(tok::less)) {
         nextToken();
         break;
       }
 
       // parseEnum falls through and does not yet add an unwrapped line as an

clang/unittests/Format/FormatTest.cpp

TEST_F(FormatTest, FormatsNamespaces) {
 
   Style.NamespaceIndentation = FormatStyle::NI_None;
   verifyFormat("template <class T>\n"
                "concept a_concept = X<>;\n"
                "namespace B {\n"
                "struct b_struct {};\n"
                "} // namespace B\n",
                Style);
+  verifyFormat("template <int I> constexpr void foo requires(I == 42) {}\n"
+               "namespace ns {\n"
+               "void foo() {}\n"
+               "} // namespace ns\n",
+               Style);
 }
 
 TEST_F(FormatTest, NamespaceMacros) {
   FormatStyle Style = getLLVMStyle();
   Style.NamespaceMacros.push_back("TESTSUITE");
 
   verifyFormat("TESTSUITE(A) {\n"
                "int foo();\n"