[GSB] Clean up and audit uses of ArchetypeResolutionKind.

Use ArchetypeResolutionKind::CompleteWellFormed whenever we need to
ask questions about the potential archetype, and
ArchetypeResolutionKind::WellFormed when we need only evaluate whether
there is a legitimate type with that name (and possibly get a handle
to it).

lib/AST/Decl.cpp

@@ -3292,8 +3292,7 @@ void ProtocolDecl::computeRequirementSignature() {
                                   LookUpConformanceInModule(module));
   builder.addGenericParameter(selfType);
   auto selfPA =
-      builder.resolveArchetype(selfType,
-                               ArchetypeResolutionKind::CompleteWellFormed);
+      builder.resolveArchetype(selfType, ArchetypeResolutionKind::WellFormed);
 
   builder.addRequirement(
          requirement,