Add Evidence to Releases GraphQL endpoint

The following discussion from !30975 (merged) should be addressed:

• @dosuken123 started a discussion: (+4 comments)

  Looking at https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/graphql/types/release_type.rb#L22, @nfriend added GraphQL support for Release entries and it include evidence_sha. It seems there is an inconsistency between Rest V4 API (w/o evidence_sha) and GraphQL (w/ evidence_sha). Would you mind explaining why evidence_sha is needed in GraphQL?