Search query builder formatter

What does this MR do and why?

Adds a format class which has two methods currently:

• size: set to 0 if count_only is true
• source_fields: sets _source to fields defined in options - from Only return ID from Elasticsearch response for ... (!152905 - merged)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

Compare the queries between the class proxy and query builder to see they're the same:

Search::Elastic::IssueQueryBuilder.build(query: '*')

is the same as

Issue.__elasticsearch__.elastic_search('*').search.definition[:body]

With count_only: true:

Search::Elastic::IssueQueryBuilder.build(query: '*', options: {count_only: true})

is the same as

Issue.__elasticsearch__.elastic_search('*', options: {count_only: true}).search.definition[:body]

Related to #461872 (closed)