Backfill graphql descriptions (part 4)

What does this MR do?

Continuation of !1923 (merged), !21164 (merged) and !21536 (merged)

Backfill some more GraphQL fields, and modify some existing ones to adhere to the standards.

Description standards:

• {x} of the {y} where possible !19233 (comment 236991402)
• Booleans framed in terms of "what does this field do" i.e. Indicates repository has a Git repository !19233 (comment 236991402)
• Always use timestamp when describing a Types::TimeType field !19233 (comment 236997153)
• No . at end of strings

Related to #31645 (closed)