Expose parser tokens_count

[ravangen]

Objective

Ability to apply max_query_string_tokens setting without breaking any existing operations.

Problem

We don't know the current distribution of the size of the tokens in existing operations.

Proposal

Expose tokens_count on Parser#tokens_count. Trigger parsing if not already done.

Outcome

To gather data, temporarily swap from the convenient GraphQL.parse to GraphQL::Language::Parser.new (or similar)

[rmosolgo]

Cool, thanks!