Add logging of service metadata during instance create/update/delete

[kathap]

Inform operators which service plan, service offering and broker is involved in service instance creation/update/deletion

• A short explanation of the proposed change: Add names of service plan, service offering and broker as logging information for service instance creation/update/deletion. This change updates fetch_writable_service_instance to eagerly load associated service_plan, service, and service_broker relationships for managed service instances. This avoids N+1 queries when accessing these associations later in the request lifecycle.

• An explanation of the use cases your change solves This change improves operator visibility by logging service plan names, offerings, and broker names during service instance creation, update, and deletion. Previously, logs only included GUIDs or IDs, requiring manual lookups or customer input to identify the service involved. With this change, operators can directly see which service is affected, making it easier to diagnose issues and support users/customers more efficiently.

• [X] I have reviewed the contributing guide

• [X] I have viewed, signed, and submitted the Contributor License Agreement

• [X] I have made this pull request to the main branch

• [X] I have run all the unit tests using bundle exec rake

• [X] I have run CF Acceptance Tests