Unicorn: add support for direct object storage of Uploads

Bring in support for direct upload to object storage for user uploads to the GitLab instance.

unicorn:

• Move bucket default(s) from minio section to appropriate lfs and uploads sections
• Add uploads section to the ConfigMap's gitlab.yml.erb
• Add documentation for uploads section
• Clean up wording of connection setting lfs and uploads

minio:

• Add gitlab-uploads bucket to defaultBuckets

Settings changed per https://docs.gitlab.com/ee/administration/uploads.html#using-object-storage

Possible: pending gitlab-org/gitlab-ce#44142, due to https://gitlab.com/gitlab-org/gitlab-ce/issues/44663#note_70634723