Remove 'stagerrm' command from EOS

As discussed in #278 (closed), we have added a new command eos evict, more powerful than eos stagerrm and intended to replace it.

After deploying an EOS version with eos evict - and changing all the operation tools, as well as FGC GC, that use it - we should remove eos stagerrm from EOS.

This issue will track that removal.