clear pg for moved out member

[JacksonYao287]

when a member is moved out of a pg, we should clean up the pg and reclaim the resource allocated to this pg, including:
1 reset all the chunk allocator and return the chunks to chunk selector so that they can be assigned to other pg
2 remove indextable of this pg
3 remove this pg from pg map
4 delete pg and related shard super blk

[xiaoxichen]

Please do consider persistency and cp. Roughly thinking I believe it is fine but need further analyze .

[JacksonYao287]

also, pls consider the crash recover

[Hooper9973]

do pg clean up in : #242