[Sema] Remove unused includes (NFC) (#141419)

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

Author: kazutakahirata

clang/lib/Sema/SemaAccess.cpp

@@ -21,7 +21,6 @@
 #include "clang/Sema/DelayedDiagnostic.h"
 #include "clang/Sema/Initialization.h"
 #include "clang/Sema/Lookup.h"
-#include "llvm/ADT/STLForwardCompat.h"
 
 using namespace clang;
 using namespace sema;

clang/lib/Sema/SemaBoundsSafety.cpp

@@ -11,7 +11,6 @@
 /// (e.g. `counted_by`)
 ///
 //===----------------------------------------------------------------------===//
-#include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Sema/Initialization.h"
 #include "clang/Sema/Sema.h"

clang/lib/Sema/SemaCUDA.cpp

@@ -22,7 +22,6 @@
 #include "clang/Sema/ScopeInfo.h"
 #include "clang/Sema/Sema.h"
 #include "clang/Sema/Template.h"
-#include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/SmallVector.h"
 #include <optional>
 using namespace clang;

clang/lib/Sema/SemaDecl.cpp

@@ -62,7 +62,6 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
-#include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/TargetParser/Triple.h"
 #include <algorithm>

clang/lib/Sema/SemaDeclAttr.cpp

@@ -58,7 +58,6 @@
 #include "clang/Sema/SemaWasm.h"
 #include "clang/Sema/SemaX86.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Demangle/Demangle.h"
 #include "llvm/IR/DerivedTypes.h"

clang/lib/Sema/SemaDeclCXX.cpp

@@ -49,7 +49,6 @@
 #include "clang/Sema/TemplateDeduction.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/ConvertUTF.h"
 #include "llvm/Support/SaveAndRestore.h"

clang/lib/Sema/SemaDirectX.cpp

@@ -9,7 +9,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Sema/SemaDirectX.h"
-#include "clang/Basic/TargetBuiltins.h"
 #include "clang/Sema/Sema.h"
 
 namespace clang {

clang/lib/Sema/SemaExpr.cpp

@@ -60,7 +60,6 @@
 #include "clang/Sema/SemaPseudoObject.h"
 #include "clang/Sema/Template.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/ConvertUTF.h"
 #include "llvm/Support/SaveAndRestore.h"

clang/lib/Sema/SemaInit.cpp

@@ -31,7 +31,6 @@
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/PointerIntPair.h"
-#include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/ErrorHandling.h"

clang/lib/Sema/SemaOpenACCAtomic.cpp

@@ -15,7 +15,6 @@
 #include "clang/Sema/SemaOpenACC.h"
 
 #include <optional>
-#include <variant>
 
 using namespace clang;