[clang] Use isa instead of dyn_cast (NFC)

clang/include/clang/AST/LambdaCapture.h

clang/include/clang/Sema/Initialization.h

clang/lib/AST/QualTypeNames.cpp

clang/lib/AST/Type.cpp

clang/lib/CodeGen/CGOpenMPRuntime.cpp

clang/lib/CodeGen/CGStmtOpenMP.cpp

clang/lib/CodeGen/CodeGenFunction.h

clang/lib/CodeGen/CodeGenModule.cpp

clang/lib/CodeGen/CoverageMappingGen.cpp

clang/lib/Sema/SemaChecking.cpp

clang/lib/Sema/SemaDecl.cpp

clang/lib/Sema/SemaDeclObjC.cpp

clang/lib/Sema/SemaExpr.cpp

clang/lib/Sema/SemaOverload.cpp

clang/lib/Sema/SemaTemplate.cpp

clang/lib/Sema/SemaType.cpp

clang/lib/StaticAnalyzer/Checkers/DynamicTypePropagation.cpp

...alyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp

...aticAnalyzer/Checkers/WebKit/UncountedCallArgsChecker.cpp

clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp