Don't spend time initializing LLVM when running the driver (#14896)

Tiny start-up time optimization noticed while looking at how we do
PrettyStackTraceProgram. Also add PrettyStackTraceProgram to a few
more of our testing tools, via the new PROGRAM_START macro.

tools/sil-func-extractor/SILFunctionExtractor.cpp

@@ -225,7 +225,8 @@ void removeUnwantedFunctions(SILModule *M, ArrayRef<std::string> MangledNames,
 }
 
 int main(int argc, char **argv) {
-  INITIALIZE_LLVM(argc, argv);
+  PROGRAM_START(argc, argv);
+  INITIALIZE_LLVM();
 
   llvm::cl::ParseCommandLineOptions(argc, argv, "Swift SIL Extractor\n");