refactor: Selection Set Template - Basic

[calvincestari]

This PR refactors the selection set template to correctly render basic deferred inline fragments. By 'basic' I mean a simple @defer directive on an inline fragment with and without a type case specification, on the same and on a different type case.

This is not intended to be a complete change set for all deferred fragments. Instead this will allow generation of a complete model for a simple deferred fragment operation so I can move on to the next piece of the stack - the executor. There are warnings in place to mark where more complex test cases are needed.

This will generate the following sections of an operation model for deferred inline fragments:

• selections
• field accessor
• fragment accessor
• root type entity

The selection set template test diff still looks like a bit of a mess so the tests to focus on are:

• Selections - Deferred Inline Fragment
• Field Accessors - Deferred Inline Fragment
• Fragment Accessors - Deferred Inline Fragment
• Root Type Entity
  • test__render_deferredTypeCase__givenDeferredInlineFragmentWithoutTypeCase_rendersRootEntityType
  • test__render_deferredTypeCase__givenDeferredInlineFragmentOnSameTypeCase_rendersRootEntityType
  • test__render_deferredTypeCase__givenDeferredInlineFragmentOnDifferentTypeCase_rendersRootEntityType

[calvincestari]

Closing this in favour of #118