[clang] Fix the location of UsingTypeLoc.

[hokein]

Summary

It is revealed by the https://reviews.llvm.org/D141280.

namespace ns { class Foo {}; }
using ns::Foo;

// Before the fix, the Location of UsingTypeLoc Foo points to the
token "class", slection on ^Foo will result in the VarDecl abc.
class Foo abc;

clang-tools-extra/clangd/unittests/SelectionTests.cpp

Case Cases[] = {
       )cpp",
        "TypedefTypeLoc"},
       {R"cpp(
         typedef int Foo;
         enum Bar : [[Fo^o]];
       )cpp",
        "TypedefTypeLoc"},
 
+      {R"cpp(
+        namespace ns { class Foo {}; }
+        using ns::Foo;
+        class [[^Foo]] foo;
+      )cpp",
+       "UsingTypeLoc"},
+
       // lambda captured var-decl
       {R"cpp(
         void test(int bar) {
           auto l = [^[[foo = bar]]] { };
         })cpp",
        "VarDecl"},
       {R"cpp(
         /*error-ok*/

clang/lib/Sema/SemaType.cpp

void VisitAutoTypeLoc(AutoTypeLoc TL) {
                                          TemplateId->NumArgs);
       SemaRef.translateTemplateArguments(TemplateArgsPtr, TemplateArgsInfo);
       for (unsigned I = 0; I < TemplateId->NumArgs; ++I)
         TL.setArgLocInfo(I, TemplateArgsInfo.arguments()[I].getLocInfo());
     }
     void VisitTagTypeLoc(TagTypeLoc TL) {
       TL.setNameLoc(DS.getTypeSpecTypeNameLoc());
     }
+    void VisitUsingTypeLoc(UsingTypeLoc TL) {
+      TL.setNameLoc(DS.getTypeSpecTypeNameLoc());
+    }
     void VisitAtomicTypeLoc(AtomicTypeLoc TL) {
       // An AtomicTypeLoc can come from either an _Atomic(...) type specifier
       // or an _Atomic qualifier.
       if (DS.getTypeSpecType() == DeclSpec::TST_atomic) {
         TL.setKWLoc(DS.getTypeSpecTypeLoc());
         TL.setParensRange(DS.getTypeofParensRange());
 
         TypeSourceInfo *TInfo = nullptr;