metrics: add gauges for fulfilled configurations

[stevvooe]

Need a better way of ascertaining whether RBACSync is healthy. Export metrics for number of fulfilled rbacsyncconfigs vs errored. This will allow detection of upstream issues with monitoring.

[stevvooe]

May want to pair this work with https://github.com/cruise-automation/rbacsync/issues/6#issuecomment-455012962 to add status reporting.

[mattlandis]

Discussed in further detail with @stevvooe offline. Documenting more details here for when this gets picked up.

Metrics in the Controller:

• rbacsync_config_status (gauge with labels) - Gauge counting the number of RBACSyncConfigs and RBACSyncClusterConfigs (type as label) and the status of the processed config.
• rbacsync_binding_status (gauge with labels) - Gauge counting the number of RoleBindings and ClusterRoleBIndings configured by the controller and their statuses [created/deleted/duplicate/error states]

Metrics in Mapper/GSuite

• rbacsync_gsuite_client_creation_status (counter with labels) - Counts the status of gsuite client creations
• rbacsync_gsuite_members_status (counter with labels) - Counts the status of calls to gsuite with labels for state - TimeoutError, NotFoundError, Cancled, UnknownError Success.
• rbacsync_gsuite_members_latency (histogram) - Histogram of the calls to gsuite for group memberships.

[mllu]

this issue was addressed in https://github.com/cruise-automation/rbacsync/pull/19 and released in https://github.com/cruise-automation/rbacsync/releases/tag/v1.2.0, we should be good to close this issue. Thanks for helping review.