[steiler]

Summary

• Adds a config-server-backed cache.Client implementation that reads last-applied config via a new config_read.ConfigReadService gRPC client instead of the local/dragonfly cache.

Pairs-with: sdcio/config-server#476
Pairs-with: sdcio/integration-tests#115

Note on integration coverage

The integration-tests job now runs tests/05-cache-backend/ (CRUD round-trip + restart-recovery) against a Cache.Type: config-server deployment via sdcio/integration-tests PR #115, which extends single.yml with cache_type/suites_to_run inputs and adds the suite itself.

Pairs-with: sdcio/integration-tests#115 supersedes the previous #113 reference: #115's branch bundles #113's config-keyring Secret fix directly (a hard, cache-backend-independent prerequisite -- without it data-server-controller hangs in ContainerCreating for any deploy) alongside the actual cache-backend suite/workflow changes, so a single paired ref now covers both concerns.