Update telemetry docs

[jsosulska]

Taking a pass at updating telemetry.md. This update is based on the search query: is:open label:theme/telemetry label:type/docs. Aims to fix #8422

This PR is deceptively large, and works best if you split out the changes into commits. I included a brief explination as to whats in the commits.

Fixes #2379-Improve interval explanation in the telemetry doc

• Moved interval explanation to the top of the guide, and included a chart as requested in the ticket. Please let me know if I missed any sinks.

Fixes #4734-Update consul memory metrics

• Included a link to the MemStat page as well as the GitHub issue for more context.

Fixes #4836-Removed node.deregistration as that isn't in state.go

• The larger ticket has been resolved per Telemetry/fix missing and stale docs #9261. There was a metric that we said we exposed node.deregistration that wasn't actually exposed, and that was deleted from the table.

partially #8986-Trim redundant language

• The ticket talks about reorganizing the metrics presentation, alphabetizing them, trimming redundant language, and adding more sections. This particular commit removes "This {measures,counts,increments}" from the descriptions, as well as adds a missing code \`` for consul.version`

Fixes #9087-Adds helpful details to telemetry on autopilot

• The original issue requests adding some direction for operators reading through this guide. I added a link to the other sections wrt leadership and raft timings.
  Fixes consul_autopilot_healthy metric is NaN #9274-Addresses NaN output in autopilot
• Adds an explicit call out to the docs about NaN being reflected on any non-leader server when prometheus metrics are requested.

[mkcp]

We went over this on zoom! Looks good!

[hashicorp-ci]

🍒 If backport labels were added before merging, cherry-picking will start automatically.

To retroactively trigger a backport after merging, add backport labels and re-run https://circleci.com/gh/hashicorp/consul/341716.

[hashicorp-ci]

🍒✅ Cherry pick of commit 277de5a onto stable-website succeeded!

[hashicorp-ci]

🍒✅ Cherry pick of commit 277de5a onto release/1.9.x succeeded!