storeliveness: add new logging channel

In https://github.com/cockroachdb/cockroach/pull/131673, we considered adding a new logging channel to consolidate all Store Liveness state transitions in one easy-to-digest place. Some concerns were brought up around adding complexity on the customer side due to having to configure this new logging channel.

We decided to punt on the new logging channel until we've had some debugging experience with store liveness and we know what logs would be useful to include there. We also thought it would be useful to include logs from other components in the new channel, for an enhanced signal. There are a couple of options:

1. Include store liveness and node liveness logs. This would be nice in providing a more comprehensive liveness signal, and will make it clear that store liveness is the replacement for node liveness (in many cases).
2. Include store liveness and lease logs. This would be nice in providing a single place to debug leader-lease related issues.

Both 1 and 2 seems hard to fit in a single logging channel, but we should see what makes sense in practice.

Jira issue: CRDB-43440