Deprecate direct access of Gitlab::Redis::Cache in favor of Rails.cache

As mentioned in https://gitlab.com/gitlab-org/gitlab-ce/issues/64794#note_193946370, we should consider deprecating the use of Gitlab::Redis::Cache.with in favor of Rails.cache because the new RedisCacheStore introduced in Rails 5.2 (https://github.com/rails/rails/pull/31134) supports a number of features that we could use:

• Supports vanilla Redis, hiredis, and Redis::Distributed (required for https://gitlab.com/gitlab-org/gitlab-ce/issues/64142)
• Supports Memcached-like sharding across Redises with Redis::Distributed (required for https://gitlab.com/gitlab-org/gitlab-ce/issues/64142)
• Fault tolerant. If the Redis server is unavailable, no exceptions are raised. Cache fetches are treated as misses and writes are dropped.

I'm not sure if we can port calls to HMSET to write_multi_entries and HMGET to read_multi_entries. We also use other Redis primitives, such as SMEMBERS and SCARD. We could punt on the problem and just using the shared state cache in some cases.

$ git grep Gitlab::Redis::Cache.with
config/initializers/7_redis.rb:Gitlab::Redis::Cache.with { nil }
lib/gitlab/action_rate_limiter.rb:      Gitlab::Redis::Cache.with do |redis|
lib/gitlab/cache/ci/project_pipeline_status.rb:          Gitlab::Redis::Cache.with do |redis|
lib/gitlab/cache/ci/project_pipeline_status.rb:          Gitlab::Redis::Cache.with do |redis|
lib/gitlab/cache/ci/project_pipeline_status.rb:          Gitlab::Redis::Cache.with do |redis|
lib/gitlab/cache/ci/project_pipeline_status.rb:          Gitlab::Redis::Cache.with do |redis|
lib/gitlab/external_authorization/cache.rb:        @access, @reason, @refreshed_at = ::Gitlab::Redis::Cache.with do |redis|
lib/gitlab/external_authorization/cache.rb:        ::Gitlab::Redis::Cache.with do |redis|
lib/gitlab/health_checks/redis/cache_check.rb:              Gitlab::Redis::Cache.with(&:ping)
lib/gitlab/markdown_cache/redis/store.rb:          Gitlab::Redis::Cache.with do |r|
lib/gitlab/markdown_cache/redis/store.rb:          results = Gitlab::Redis::Cache.with do |r|
lib/gitlab/shard_health_cache.rb:      Gitlab::Redis::Cache.with { |redis| redis.del(HEALTHY_SHARDS_KEY) }
lib/gitlab/shard_health_cache.rb:      Gitlab::Redis::Cache.with do |redis|
lib/gitlab/shard_health_cache.rb:      Gitlab::Redis::Cache.with { |redis| redis.smembers(HEALTHY_SHARDS_KEY) }
lib/gitlab/shard_health_cache.rb:      Gitlab::Redis::Cache.with { |redis| redis.sismember(HEALTHY_SHARDS_KEY, shard_name) }
lib/gitlab/shard_health_cache.rb:      Gitlab::Redis::Cache.with { |redis| redis.scard(HEALTHY_SHARDS_KEY) }
lib/tasks/cache.rake:      Gitlab::Redis::Cache.with do |redis|
spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb:      read_sha, read_status = Gitlab::Redis::Cache.with { |redis| redis.hmget(cache_key, :sha, :status) }
spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb:      sha, status, ref = Gitlab::Redis::Cache.with { |redis| redis.hmget(cache_key, :sha, :status, :ref) }
spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb:      sha, status = Gitlab::Redis::Cache.with { |redis| redis.hmget(cache_key, :sha, :status) }
spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb:      Gitlab::Redis::Cache.with do |redis|
spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb:      sha, status, ref = Gitlab::Redis::Cache.with { |redis| redis.hmget("projects/#{empty_project.id}/pipeline_status", :sha, :status, :ref) }
spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb:      Gitlab::Redis::Cache.with do |redis|
spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb:          Gitlab::Redis::Cache.with do |redis|
spec/lib/gitlab/cache/ci/project_pipeline_status_spec.rb:        key_exists = Gitlab::Redis::Cache.with { |redis| redis.exists(cache_key) }
spec/lib/gitlab/discussions_diff/highlight_cache_spec.rb:        found = Gitlab::Redis::Cache.with { |r| r.get(full_key) }
spec/lib/gitlab/external_authorization/cache_spec.rb:    Gitlab::Redis::Cache.with do |redis|
spec/lib/gitlab/external_authorization/cache_spec.rb:    Gitlab::Redis::Cache.with do |redis|
spec/lib/gitlab/github_import/caching_spec.rb:      values = Gitlab::Redis::Cache.with { |r| r.smembers(key) }
spec/lib/gitlab/github_import/caching_spec.rb:        found = Gitlab::Redis::Cache.with { |r| r.get(full_key) }
spec/lib/gitlab/github_import/caching_spec.rb:      found_ttl = Gitlab::Redis::Cache.with { |r| r.ttl(key) }
spec/lib/gitlab/markdown_cache/redis/extension_spec.rb:    Gitlab::Redis::Cache.with do |r|
spec/lib/gitlab/markdown_cache/redis/extension_spec.rb:      results = Gitlab::Redis::Cache.with do |r|
spec/lib/gitlab/markdown_cache/redis/store_spec.rb:    Gitlab::Redis::Cache.with do |r|
spec/lib/gitlab/markdown_cache/redis/store_spec.rb:    Gitlab::Redis::Cache.with do |r|
spec/services/git/branch_push_service_spec.rb:      Gitlab::Redis::Cache.with { |conn| conn.flushall }
spec/services/git/branch_push_service_spec.rb:      Gitlab::Redis::Cache.with { |conn| conn.flushall }
spec/support/redis/redis_helpers.rb:    Gitlab::Redis::Cache.with(&:flushall)
spec/support/shared_examples/unique_ip_check_shared_examples.rb:    Gitlab::Redis::Cache.with(&:flushall)