This CL solve the issue #3105
I add a new temporary table state WAITING_STABLE.
When an alter job is ready to start, it checks whether the table is stable. If it is not stable,
the table state is set to WAITING_STABLE. In this state, the tablet repair logic will continue to
repair the tablet until the table becomes stable.
After that, the table state will be reset to SCHEMA_CHANGE/ROLLUP and alter operations will begin.
This is just a temporary state, it does not need to be persistent, and only the master FE can see this state.
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