Remove GraphQL GlobalIDType compatibility layer

In !36209 (merged) a compatibility layer was introduced to allow us to change the types of arguments from ID_TYPE to GlobalIDType[T]. This requires us to be careful and add lots of explicit coercions.

This issue is for the removal of the compatibility layer once the deprecation cycle has been run, and all stakeholders informed.

During %14.8

Manage deprecation: #352832 (closed)

• Update the deprecation list including this changes https://docs.gitlab.com/ee/update/deprecations.html
  • see: !80636 (merged)
• Update the milestone to %14.10

During %14.10 or %15.0

• Remove the compatibility layer introduced in !36209 (merged), which overrides the type equality check.
• Remove all the explicit coercions, marked where possible with TODOs
• Ensure arguments are required: as appropriate (see !46491 (comment 439169712))