This is the first step of
FLINK-14106, including all the major changes inside SlotManager and changes to the RM/SM interfaces, except changes for metrics and status.
At the end of this step, SlotManager should allocate resource from ResourceManager with a WorkerResourceSpec, instead of slot ResourceProfile. At this step, the WorkerResourceSpec will not be used, and the active RMs will always use `ActiveResourceManager#taskExecutorProcessSpec` for requesting TMs. We will change that in subsequent steps.