[hotfix][cdc-connector][test] Sleep to wait for the assign status to INITIAL_ASSIGNING_FINISHED so that newly added table won't be stuck.

[loserwang1024]

Currenly, tests are often stuck in removing table test . The reason is:

1. when getting all the data of snapshot split, the assigned status maybe still not switched from INITIAL_ASSIGNING to INITIAL_ASSIGNING_FINISHED. (If stop and restart job now, the table won't be removed from enumerator.)
2. when restarted, the job is still be snapshot phase, and table will be read again. It is not what the testRemoveTablesOneByOne wants.
3. Disable enable backfill test in sqlserver cdc connector until FLINK-34833 is resolved

Thus, this pr will wait 1s until the assigned status is INITIAL_ASSIGNING_FINISHED.

[leonardBang]

+1

[loserwang1024]

The mysql test is failed and I fixed it, run it sucessfule in my CI, https://github.com/loserwang1024/flink-cdc-connectors/actions/runs/14237185479

@leonardBang , Could you please help to rerun this mysql test after my modification.

[leonardBang]

The mysql test is failed and I fixed it, run it sucessfule in my CI, https://github.com/loserwang1024/flink-cdc-connectors/actions/runs/14237185479

@leonardBang , Could you please help to rerun this mysql test after my modification.

Sure