migrate to Buildhub2

[willkg]

crashstop uses Buildhub:

crashstop/crashstop/buildhub.py

Line 12 in d9f3bad

URL = 'https://buildhub.prod.mozaws.net/v1/buckets/build-hub/collections/releases/search'

Buildhub is deprecated and will be decommissioned in July. See mozilla-services/buildhub#532 for details.

There are API docs here:

https://buildhub2.readthedocs.io/en/latest/user.html

This issue covers migrating pushlog-addon to Buildhub2.

[willkg]

@calixteman There's crashstop and crashstop-addon. I see you updated crashstop-addon. Does crashstop also need to be updated or is it not used anymore?