swift-module-digester: refactor the ABI/API diagnostics to use DiagnosticEngine. NFC (#18957)

Before this patch, we used to define tooling-specific diagnostics. With adding more
checking logics, we found this mechanism hard to extend. This patch
eliminates the home-made diagnostics model to use the one from compiler, which provides
several benefits: less boiler-templates, better integration with DiagnosticConsumer,
and easy ordering of detected issues.

tools/swift-api-digester/ModuleAnalyzerNodes.h

@@ -139,6 +139,7 @@ struct CheckerOptions {
   bool ABI;
   bool Verbose;
   bool AbortOnModuleLoadFailure;
+  bool PrintModule;
   StringRef LocationFilter;
 };
 
@@ -303,6 +304,7 @@ public:
   bool hasDeclAttribute(DeclAttrKind DAKind) const;
   bool isStatic() const { return IsStatic; };
   StringRef getGenericSignature() const { return GenericSig; }
+  StringRef getScreenInfo() const;
 };
 
 class SDKNodeRoot: public SDKNode {