[unittests] Add missing includes (#65681)

There are missing include and using in TextStubTests and
AsmPrinterDwarfTest and they causes build failures when using vanilla
GoogleTest v1.14.0. This patch fixes this issue.

Author: zeroomega

llvm/unittests/CodeGen/AsmPrinterDwarfTest.cpp

@@ -20,6 +20,7 @@
 
 using namespace llvm;
 using testing::_;
+using testing::DoAll;
 using testing::InSequence;
 using testing::SaveArg;
 

llvm/unittests/TextAPI/TextStubHelpers.h

@@ -6,6 +6,7 @@
 //
 //===-----------------------------------------------------------------------===/
 
+#include "llvm/ADT/SmallString.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/TextAPI/InterfaceFile.h"
 #include <algorithm>