Add Traffic Ops API Testing Monitor Support

[rob05c]

Currently, the TO API Tests don't support Traffic Monitors. This makes it impossible to write integration tests for endpoints that call out to Monitors.

We need to add Monitor support, so we can test the Monitor endpoints.

This may be as simple as adding a few fixtures and configs, or it may be rather difficult. To begin with, someone needs to investigate or prototype it, to find out how much work it's going to be.

See also https://github.com/apache/trafficcontrol/issues/3348

I'm submitting a ...

• [ ] bug report
• [x] new feature / enhancement request
• [ ] improvement request (usability, performance, tech debt, etc.)
• [ ] other

Traffic Control components affected ...

• [ ] CDN in a Box
• [ ] Documentation
• [ ] Grove
• [ ] Traffic Control Client
• [x] Traffic Monitor
• [ ] Traffic Ops
• [ ] Traffic Ops ORT
• [ ] Traffic Portal
• [ ] Traffic Router
• [ ] Traffic Stats
• [ ] Traffic Vault
• [ ] unknown

Current behavior:

API Tests don't support Monitors.

Expected / new behavior:

API Tests support Monitors, and support tests that make requests to them.

Minimal reproduction of the problem with instructions:

Write an API Test that requests a Monitor endpoint.

Anything else:

[mitchell852]

added high impact label as this blocks any testing for certain TO API endpoints.