R1:aa3b582c7b72

Remove "set password" from `bin/accountadmin` and let `bin/auth recover` recover anyone

Summary:
Ref T13043. This cleans some things up to prepare for moving account passwords to shared infrastructure.

Currently, the (very old, fairly unusual) `bin/accountadmin` tool can set account passwords. This is a bit weird, generally not great, and makes upgrading to shared infrastructure more difficult. Just get rid of this to simplify things. Many installs don't have passwords and this is pointless and unhelpful…