ref(cells): Introduce new cell config keys

[lynnagara]

introduce config that isn't used yet.
once this config is set in prod, we can flip usages in the codebase

[github-actions]

Backend Test Failures

Failures on e94407e in this run:

tests/sentry/management/commands/test_generate_controlsilo_urls.py::TestGenerateControlsiloUrls::test_no_missing_urls — log

tests/sentry/management/commands/test_generate_controlsilo_urls.py:70: in test_no_missing_urls
    assert line in current_state, msg
E   AssertionError: 
E                 New control silo URL patterns detected!
E     
E                 The pattern:   new RegExp('^api/0/organizations/[^/]+/pipeline/[^/]+/$'),
E     
E                 Does not exist in the current pattern inventory. You should regenerate
E                 the pattern inventory with:
E     
E                 cd ../getsentry
E                 getsentry django generate_controlsilo_urls --format=js --output=../sentry/static/app/data/controlsiloUrlPatterns.ts
E     
E                 This command needs to be run in a getsentry environment
E                 in order to not lose patterns that are important for sentry.io
E                 
E   assert "  new RegExp('^api/0/organizations/[^/]+/pipeline/[^/]+/$')," in "// This is generated code.\n// To update it run `getsentry django generate_controlsilo_urls --format=js --output=/pat...gExp('^extensions/discord/link-identity/[^/]+/$'),\n  new RegExp('^extensions/discord/unlink-identity/[^/]+/$'),\n];\n"