controller: Add INFO log-level log when a topic configuration was changed

Who is this for and what problem do they have today?

This is for Redpanda users who need to troubleshoot and check when a configuration was changed.

What are the success criteria?

INFO level to log when a topic configuration was changed and record the previous value and the newly updated value. If possible, add who(client IP and user) changed the configuration

Why is solving this problem impactful?

Currently, we have INFO-level logs when a new topic is created. The log includes default configuration values. However, there are no logs to check when a configuration was changed. As a result, we always have to need run rpk command to check current configuration values. But, the rpk command cannot tell when the configuration was updated. Sometimes rpk command fails when a cluster is not stable. For example, the nodes are repeatedly restarted as a bug, it is almost impossible to check the configurations.

Additional notes

N/A

JIRA Link: CORE-1115

Start by locating the existing INFO log for topic creation and the code path that updates topic configuration. Check whether the update path exposes the previous and new values and client identity, then add logging and tests showing the change is recorded at INFO level.