[ASTMatchers] Remove unused includes (NFC) (#142407)

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/ASTMatchers/ASTMatchersInternal.cpp

@@ -26,13 +26,10 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
-#include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/Support/raw_ostream.h"
-#include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <optional>

clang/lib/ASTMatchers/Dynamic/Parser.cpp

@@ -19,7 +19,6 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/ManagedStatic.h"
-#include <algorithm>
 #include <cassert>
 #include <cerrno>
 #include <cstddef>

clang/lib/ASTMatchers/Dynamic/Registry.cpp

@@ -17,13 +17,11 @@
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/ASTMatchers/Dynamic/Diagnostics.h"
 #include "clang/ASTMatchers/Dynamic/VariantValue.h"
-#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
-#include <iterator>
 #include <memory>
 #include <optional>
 #include <set>

clang/lib/ASTMatchers/Dynamic/VariantValue.cpp

@@ -13,7 +13,6 @@
 
 #include "clang/ASTMatchers/Dynamic/VariantValue.h"
 #include "clang/Basic/LLVM.h"
-#include "llvm/ADT/STLExtras.h"
 #include <optional>
 
 namespace clang {

clang/lib/ASTMatchers/GtestMatchers.cpp

@@ -16,11 +16,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/ASTMatchers/GtestMatchers.h"
-#include "clang/AST/ASTConsumer.h"
-#include "clang/AST/ASTContext.h"
-#include "clang/AST/RecursiveASTVisitor.h"
-#include "clang/ASTMatchers/ASTMatchFinder.h"
-#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringRef.h"
 
 namespace clang {