Build libSwiftStaticMirror as a standalone library with minimal required dependencies.

This separates it from `libSwiftScan` and allows us to build this library without building much of the rest of the compiler.

Also refactor `utils/build-parser-lib` into `utils/build-tooling-libs` which builds both SwiftSyntaxParser and SwiftStaticMirror.

include/swift/DependencyScan/StringUtils.h

@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "swift-c/DependencyScan/DependencyScan.h"
+#include "swift-c/CommonString/CommonString.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
 #include <string>
@@ -18,7 +18,7 @@
 
 //=== Private Utility Functions--------------------------------------------===//
 namespace swift {
-namespace dependencies {
+namespace c_string_utils {
 
 /// Create null string
 swiftscan_string_ref_t create_null();