Query: Introduce FromSqlQueryingEnumerable for non composed FromSql

[smitpatel]

• Move ReaderColumns to RelationalCommandCache

[ErikEJ]

What problem does this fix?

[smitpatel]

@ErikEJ - It does not fix any problem directly. Currently we have QueryingEnumerable which works for both non composed FromSql and regular query too. The "optional" index map parameter lies around. It was ok refactor.
But now I also need to add a QueryingEnumerable for split query scenario which would actually materialize quite differently. So it seemed that splitting each in separate Enumerable is simpler to process. (See #21181 which combines different phases of processing shaper into one #21189 which introduces 3rd kind of QueryingEnumerable).