Latency Monitoring for internal alerts

[apizzuto]

Create a latency monitoring page with test alerts for the internal track and cascade followup, similar to the one we had for O3 GW (https://icecube.wisc.edu/~apizzuto/O3_followup/O3_followup.html)

[apizzuto]

Also maybe include latency monitoring for GRBs, and definitely revive the latency monitoring for O4

[apizzuto]

When running on "mocks", be sure to use the sample skymaps that have already been provided in fast_response/sample_skymaps.
That's the only reason that they're there, so I'm going to close the other issue related to sample_skymaps