SIL: remove the SILOpenedArchetypesTracker

Instead, put the archetype->instrution map into SIlModule.

SILOpenedArchetypesTracker tried to maintain and reconstruct the mapping locally, e.g. during a use of SILBuilder.
Having a "global" map in SILModule makes the whole logic _much_ simpler.

I'm wondering why we didn't do this in the first place.

This requires that opened archetypes must be unique in a module - which makes sense. This was the case anyway, except for keypath accessors (which I fixed in the previous commit) and in some sil test files.

lib/Serialization/ModuleFile.cpp

@@ -91,8 +91,7 @@ static bool isTargetTooNew(const llvm::Triple &moduleTarget,
 }
 
 ModuleFile::ModuleFile(std::shared_ptr<const ModuleFileSharedCore> core)
-    : Core(core),
-      DeserializedTypeCallback([](Type ty) {}) {
+    : Core(core) {
   assert(!core->hasError());
 
   DeclTypeCursor = core->DeclTypeCursor;