Implement some sort of limit on how many part exports can be schedule in a given replica

[arthurpassos]

AS of now, it is memory bound. The user can schedule as many as it wants, and depending on executor pool size, it will execute them.

This is a problem because it does not offer us any mechanism to prevent a single replica from locking ALL parts for a given export partition at once and leaving other replicas with nothing to do.

It is not as simple as checking the executor pool size because of TOCTOU. Maybe we need an extra layer aside from the executor pool?

[arthurpassos]

There is another problem: the memory bound queue / partition export context we have is per table, but the moves executor is per server.