Enable even more frozen string in lib/gitlab

Enables frozen string for the following:

* lib/gitlab/fogbugz_import/**/*.rb
* lib/gitlab/gfm/**/*.rb
* lib/gitlab/git/**/*.rb
* lib/gitlab/gitaly_client/**/*.rb
* lib/gitlab/gitlab_import/**/*.rb
* lib/gitlab/google_code_import/**/*.rb
* lib/gitlab/gpg/**/*.rb
* lib/gitlab/grape_logging/**/*.rb
* lib/gitlab/graphql/**/*.rb
* lib/gitlab/graphs/**/*.rb
* lib/gitlab/hashed_storage/**/*.rb
* lib/gitlab/health_checks/**/*.rb

Partially address gitlab-org/gitlab-ce#47424.

changelogs/unreleased/frozen-string-lib-gitlab-even-more.yml

+---
+title: Enable even more frozen string in lib/gitlab/**/*.rb
+merge_request:
+author: gfyoung
+type: performance

lib/gitlab/fogbugz_import/client.rb

+# frozen_string_literal: true
+
 require 'fogbugz'
 module Gitlab

lib/gitlab/fogbugz_import/importer.rb

+# frozen_string_literal: true
+
 module Gitlab
   module FogbugzImport
     class Importer

lib/gitlab/fogbugz_import/project_creator.rb

+# frozen_string_literal: true
+
 module Gitlab
   module FogbugzImport
     class ProjectCreator

lib/gitlab/fogbugz_import/repository.rb

+# frozen_string_literal: true
+
 module Gitlab
   module FogbugzImport
     class Repository

lib/gitlab/gfm/reference_rewriter.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Gfm
     ##

lib/gitlab/gfm/uploads_rewriter.rb

+# frozen_string_literal: true
+
 require 'fileutils'
 module Gitlab

lib/gitlab/git/attributes_at_ref_parser.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     # Parses root .gitattributes file at a given ref

lib/gitlab/git/attributes_parser.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     # Class for parsing Git attribute files and extracting the attributes for

lib/gitlab/git/blame.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     class Blame

lib/gitlab/git/blob.rb

+# frozen_string_literal: true
+
 # Gitaly note: JV: seems to be completely migrated (behind feature flags).
 module Gitlab

lib/gitlab/git/branch.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     class Branch < Ref

lib/gitlab/git/commit.rb

+# frozen_string_literal: true
+
 # Gitlab::Git::Commit is a wrapper around Gitaly::GitCommit
 module Gitlab
   module Git

lib/gitlab/git/commit_stats.rb

+# frozen_string_literal: true
+
 # Gitlab::Git::CommitStats counts the additions, deletions, and total changes
 # in a commit.
 module Gitlab

lib/gitlab/git/compare.rb

+# frozen_string_literal: true
+
 # Gitaly note: JV: no RPC's here.
 module Gitlab

lib/gitlab/git/conflict/file.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     module Conflict

lib/gitlab/git/conflict/parser.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     module Conflict

lib/gitlab/git/conflict/resolution.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     module Conflict

lib/gitlab/git/conflict/resolver.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     module Conflict

lib/gitlab/git/diff.rb

+# frozen_string_literal: true
+
 module Gitlab
   module Git
     class Diff