Query: Cleanup pattern matching to FromSql method in Core

[smitpatel]

Issues:
Our query roots are entityQueryables in expression tree that is how we identify starting entityType during navigation expansion.

• FromSql is also query root but relational method so core does not know about it. So query filters are supposed to be applied after FromSql method but does not happen.
  Few possible solutions:
• Make FromSql a query root in the tree by introducing FromSqlEntityQueryable
  • FromSql method has parameters which needs to be funcletized. If FromSqlEntityQueryable is injected when the method is called then funcletizer needs to know about it and requires relational specific version.
  • If we inject FromSqlEntityQueryable after funcletizer part then FromSql in defining query wouldn't be changed. (The injector would be relational specific and navigation expansion cannot run a relational visitor).
• Relational specific nav expansion which is only for to inject query root for FromSql method. This requires us to expose a lot of private code in nav expansion publicly.

For now, it is pattern matching on method in core level (since we cannot use actual MethodInfo). Given it is our own method, chances of it being broken is very low.