Spec edits for incremental delivery, Validation

[robrichard]

Extracted from the full PR (#1110) and targeting an integration branch to aid in review.

Helpful reference material:

• Response format examples: New response format (June 2023) defer-stream-wg#69
• Glossary: Glossary defer-stream-wg#106 (comment)
• GraphQL Conf talk: https://www.youtube.com/watch?v=LEyDeNoobT0

[benjie]

Let's split this up into a @stream and @defer rule:

Suggested change

	** Formal Specification **
	- For every {directive} in a document.
	- Let {directiveName} be the name of {directive}.
	- Let {mutationType} be the root Mutation type in {schema}.
	- Let {subscriptionType} be the root Subscription type in {schema}.
	- If {directiveName} is "defer" or "stream":
	- The parent type of {directive} must not be {mutationType} or
	{subscriptionType}.
	**Formal Specification**
	- For each `@stream` {directive} in the document:
	- Let {field} be the field to which the directive is applied.
	- The parent type of {field} must not be the {`mutation`} _root
	operation type_ or the {`subscription`} _root operation type_.

For defer it's on fragments so it's a little different. I'm not a big fan of this suggested edit, it's inspired by https://spec.graphql.org/draft/#sec-Fragment-Spread-Type-Existence but I feel like maybe we should branch on inline fragment vs named fragment spread.

- For each `@defer` {directive} in the document:
  - Let {fragmentType} be the target type of the fragment spread to which {directive} is applied.
  - {fragmentType} must not be the {`mutation`} _root
    operation type_ or the {`subscription`} _root operation type_.

[benjie]

Suggested change

	The defer and stream directives are not allowed to be used on root fields of the
	mutation or subscription type.
	The `@defer` and `@stream` directives are not allowed to be used on root fields of the
	mutation or subscription type.

[benjie]

Suggested change

	** Formal Specification **
	**Formal Specification**