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/swift-api-digester/swift-api-digester.cpp

@@ -3610,7 +3610,8 @@ static int deserializeSDKDump(StringRef dumpPath, StringRef OutputPath) {
 }
 
 int main(int argc, char *argv[]) {
-  INITIALIZE_LLVM(argc, argv);
+  PROGRAM_START(argc, argv);
+  INITIALIZE_LLVM();
 
   llvm::cl::ParseCommandLineOptions(argc, argv, "Swift SDK Digester\n");
   CompilerInvocation InitInvok;