ui/admin: add service metrics data table

[KatieMSB]

• Identified the issue which this PR solves.
• Read the CONTRIBUTING document.
• Code builds clean without any errors or warnings.
• Added appropriate tests for any new functionality.
• All new and existing tests passed.
• Added comments in the code, where necessary.
• Ran make check to catch common errors. Fixed any that came up.

Description:
This PR adds part of the service metrics ui work that includes overall metrics for all services and a table of all services.
Metrics include:

• Total Services
• Services with empty Escalation Policies
• Services without Integration Keys and Heartbeat Monitors
• Services with stale Alerts (acknowledged alerts older than 2 months)
• Services nearing or at the Unacknowledged Alert Limit

Which issue(s) this PR fixes:
Part of #3057

Out of Scope:

• filtering
• integration key/escalation policy target metrics breakdowns

Screenshots:

[tony-tvu]

LGTM

[Forfold]

As a subheader under Services, could we maybe have some loading text, such as "Loading... This may take a minute."

Also, this could maybe be iterated on later, but thinking about the top cards to be more responsive for various browser sizes. Maybe switch to xs={4} sm={2.4} or something?

Last thing, is perhaps setting the height to the top cards to 100% of their container, so their heights all match:

[ethan-haynes]

LGTM 👍