this JIRA tracks the update of ServerCrashProcedure to interact with assignment procedures. This is very critical (and most tricky part of) work that deals with dead region server when assignment is happening.
- remove region server queue when the region server is dead
- notify assignment procedures that are doing assignment operation in the dead server
- assign regions in dead server to other RS (we have to deal with RIT, deal with in-progress table DDL)