PurgeAttribute leaves orphaned expiration lookup entries

## Summary of Bug The `PurgeAttribute` keeper method (in x/attribute) deletes attribute records, and decrements the name-address lookup counter, but does not delete any attribute expiration-lookup entries. ## Proposal Update the `PurgeAttribute` keeper method to call `deleteAttributeExpireLookup`. Also, while in there, make it emit events similar to `DeleteAttribute`. ____ ## For Admin Use - [ ] Not duplicate issue - [ ] Appropriate labels applied - [ ] Appropriate contributors tagged - [ ] Contributor assigned/self-assigned