Summary:
Add testing to determine if automatic mode bootstrapping without
sequences works.

That is, I added the needed testing infrastructure to be able to do a bootstrap in the xCluster integration tests.  This includes:
  * ability to create two internal mini cluster universes and use backup and restore between them
    * this uses yb-controller
      * which in turn requires adjusting /varz output so yb-controller works correctly
      * as part of this renamed a poorly named TEST flag, TEST_mini_cluster_mode, that did only part of the needed job
    * ensured that log prefixes for the YB controllers are correct and distinct
      * had to fix the logging daemon to get the interleaving of output correct
  * added test that plain (e.g., no sequences) automatic mode bootstrapping works
  * fixed a bug that prevented automatic replication bootstrapping from working
  * discovered in the process that we have a bug where automatic replication doesn't work with no tables; created a disabled test for this and made an issue to get it fixed
  * along the way did a bit of cleanup -- e.g., removing obviously unused includes, fixing some names

Fixes #24889
Jira: DB-14011

Test Plan:
```
ybd --cxx-test xcluster_ddl_replication-test --gtest_filter '*.Bootstrapping'
```

I verified that if I remove the bug fix for automatic replication bootstrapping, the test indeed fails.

```
ybd --cxx-test pg_master_failover-test --test-args '' >& /tmp/generic.mdl.log
ybd --cxx-test cql-backup-test --test-args '' >& /tmp/generic.mdl.log
```

Reviewers: jhe, xCluster, hsunder

Reviewed By: jhe

Subscribers: loginov, yql, ybase, esheng

Differential Revision: https://phorge.dev.yugabyte.com/D39944