Guaranteed priority of Hot Region Operator

## Problem Summary
In a `bluk_insert` senario. the data's growth only in 3 TiKVs.

## Detail Information
There are many hot regions. but seems no load balance.

Opterators:
create:

many operator cancel about `hot peer move`:

Region Health:

## Root Cause Analyze
We can see the operator of the hot region actually created. but it cancels immediately. the Operator may reach store limit because we can see the balance region opm is 45, which means the 3 TiKV store limit about `remove peer` is run out.

## Expect
We have high priority about the hot region, we should guarantee it can be running rather than all store limit consumed by balance region.