v3: cleanup common

• API CHANGE: Fetching a file/shorten in the Admin API returns the proper model JSON instead of mirroring the database tables
  • Related: remove api.common.fetch in favor of using the File/Shorten models
• Add Timer so we don't need to repeat the same time.monotonic() logic all the time
• Split violet-specific functions from api.common.profile to api.common.violet_jobs
• Move api.common.profile.gen_user_shortname => User.generate_shortname
• Move api.common.common.calculate_hash => api.common.utils.calculate_hash
• Move api.common.gen_shortname => api.shortname.generate_shortname
• Remove unused functions from api.common.utils
• Remove get_user_domain_info
• Use models on resolve_domain
• Move api.common.common.calculate_hash => api.common.utils.calculate_hash
• Move api.common.utils.LockStorage to api.locks
• Move api.common.common.get_tags => Tag.fetch_all_tags
• Make api.permissions.domain_permissions use Domain model
• Remove unused get_domain_shorten, get_domain_file from api.storage
• Remove unused functions/constants from tests
• Fix typo in test_domain_create