[feature branch; do not merge] Metadata Phase 2

[krivard]

Overview

Collected changes for metadata phase 2. We'd like to roll this out all at once instead of incrementally, so we'll accumulate changes here and merge it when everybody's done.

• Closes Show or summarize available years in table descriptions #4586
• Closes Show whether the data is currently being collected or not in table descriptions #4587
• Closes Hourly output tables claim they are denormalized when they are not #4526
• May close Metadata Phase 2: Table Description Refinements #4585

What problem does this address?

What did you change?

Documentation

Make sure to update relevant aspects of the documentation:

• Update the release notes: reference the PR and related issues.
• Update relevant Data Source jinja templates (see docs/data_sources/templates).
• Update relevant table or source description metadata (see src/metadata).
• Review and update any other aspects of the documentation that might be affected by this PR.

Testing

How did you make sure this worked? How can a reviewer verify this?

To-do list

• If updating analyses or data processing functions: make sure to update row count expectations in dbt tests.
• Run make ci locally to ensure that the merge queue will accept your PR.
• Review the PR yourself and call out any questions or issues you have.
• For PRs that change the PUDL outputs significantly, run the full ETL locally and then run the data validations using dbt. If you can't run the ETL locally then run the build-deploy-pudl GitHub Action manually and ensure that it succeeds.