Add solver endpoint metrics

[bgins]

General Description

Implement and export solver endpoint metrics.

Which system(s) or functionality does this affect

This work impacts the solver and observability systems.

Describe the changes, and how this affects/ interacts with each system.

Let's add some endpoint metrics to track requests on the solver server. We should include:

• Time spent on requests per endpoint
• Successful request counts
• Failed request counts
• Possibly more

There may be some auto-instrumentation for gorilla mux to auto-instrument or we can manually instrument to track this activity.

The changes will be to the solver code and new dashboards on the observability server.