feat(cloud monitoring): add support for cloud monitoring suppressions

This adds support for Cloud Monitoring suppressions.

It provides a couple of basic functions:
- getEntities to list all entities on your account,
- getEntityIdsByRegexp to get all the entity ids whose label matches a specific regexp (useful when entity labels are set to server hostnames and you want to get i.e. all your api servers or all your servers in a region)
- createEntitiesSuppression to create a suppression on an array of entity ids,
- deleteSuppression to delete a suppression.
it would be interesting to add a metric here. might be useful to keep track of accounts with no entities.