Add GetJobCountAsync to BackWaveMonitor, and add Attempt filter to JobQuery

[DCarlson12]

It would be a nice addition to have a Count counterpart to the ListJobsAsync query method on BackWaveMonitor to aggregate quick statistics on particular jobs with filters like ListJobsAsync provides via JobQuery. My proposal would be a method GetJobCountAsync returning a long that takes the same existing JobQuery filter. Additionally, similar to how Hangfire categorizes retries, adding an Attempt filter combined with the JobState.Scheduled to JobQuery could quickly help identify jobs in a scheduled state with an attempt value greater than 0 (i.e. Retrying) since it doesn’t have its own state. Without this it is very unclear from the dashboard which jobs are having issues at a quick glance. Relying on telemetry or observers to know this doesn’t feel quite right for a trivial query on the job tables.