Ensure all `StorageVersion`s on Rococo/Westend are correct and migration hooks pass (#7251)

* set fastunstake storage version

* fix configration migration hooks

* set missing rococo versions

* remove child bounties version set

* future proof this configuration migration

* simplify rococo migration

* simplify westend version migration

* typo

* restore missing comments

* set configuration storage version correctly

* remove redundant preupgrade version check

* fix version checks

* remove redundant comment