[Dreamhost] Update regions after migration

[sa7mon]

https://help.dreamhost.com/hc/en-us/articles/32254965300372-DreamObjects-cluster-differences

DreamHost is currently in the process of migrating DreamObjects to a new hardware platform.

us-east-1 currently exists
us-east-5 is being added.

Rules for bucket naming in new region: https://help.dreamhost.com/hc/en-us/articles/115001494772-DreamObjects-Bucket-Names

Update regioncheck.go with a better method of parsing region names from the support page(s).