[Docs] add time & eliminate hard-to-measure metrics

[bryanchriswhite]

Summary

• Add a column for "time" to the service metrics tables with :question: where applicable.
• Remove :question: where measurement is not feasible at the specified resolution.
  • Correlating load timing/scaling with process-level CPU metering can be used to derive sub-process CPU metrics (e.g. req./res. processing).

Issue

• 432

• 449

Type of change

Select one or more:

• [ ] New feature, functionality or library
• [ ] Bug fix
• [ ] Code health or cleanup
• [x] Documentation
• [ ] Other (specify)

Testing

• [ ] Unit Tests: make go_develop_and_test
• [ ] LocalNet E2E Tests: make test_e2e
• [ ] DevNet E2E Tests: Add the devnet-test-e2e label to the PR. THIS IS VERY EXPENSIVE, so only do it after all the reviews are complete.
• [ ] Documentation changes: make docusaurus_start

Sanity Checklist

• [ ] I have tested my changes using the available tooling
• [ ] I have commented my code
• [ ] I have performed a self-review of my own code; both comments & source code
• [ ] I create and referenced any new tickets, if applicable
• [ ] I have left TODOs throughout the codebase, if applicable