release-24.1: dbconsole: overload page improvements

[blathers-crl]

Backport 7/7 commits from #123522 on behalf of @aadityasondhi.

/cc @cockroachdb/release

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This PR contains a series of improvements to the overload page of the DB console as part of #121574. It is separated into multiple commits for ease of review.

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dbconsole: remove non useful charts on the overload page

In investigations, we have found that the following charts are not
useful and frequently cause confusion:

• Admission work rate
• Admission Delay rate
• Requests Waiting For Flow Tokens

Informs #121572

Release note (ui change): This patch removes "Admission Delay Rate",
"Admission Work Rate", and "Requests Waiting For Flow Tokens". These
charts often cause confusion and are not useful for general overload
investigations.

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dbconsole: reorder overload page metrics for better readability

This patch reorders the existing metrics in a more usable order:

1. Metrics to help determine which resource is constrained (IO, CPU)
2. Metrics to narrow down which AC queues are seeing requests waiting
3. More advanced metrics about the system health (goroutine scheduler,
   L0 sublevels, etc.)

Informs #121572.

Release note (ui change): Reordering of metrics on the overload page to
help categorizing them better. They are roughly in the following order:

1. Metrics to help determine which resource is constrained (IO, CPU)
2. Metrics to narrow down which AC queues are seeing requests waiting
3. More advanced metrics about the system health (goroutine scheduler,
   L0 sublevels, etc.)

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dbconsole: include better names and descriptions for overload page
This patch improves the metric descriptions for the metrics on the
overload page.

Fixes #120853.

Release note (ui change): The overload page now includes descriptions for all
metrics.

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dbconsole: additional higher granularity metrics for overload

This patch adds additional metrics to the overload page that allow for
more granular look at the system:

• cr.store.storage.l0-sublevels
• cr.node.go.scheduler_latency-p99.9

Informs #121572.

Release note (ui change): Two additional metrics on the overload page
for better visibility into overloaded resources:

• cr.store.storage.l0-sublevels
• cr.node.go.scheduler_latency-p99.9

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dbconsole: split Admission Queue graphs to avoid overcrowding

Informs #121572.

Release note (ui change): There are now 4 graphs for Admission Queue
Delay:

1. Foreground (regular) CPU work
2. Store (IO) work
3. Background (elastic) CPU work
4. Replication Admission Control, store overload on replicas

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dbconsole: add elastic store metric to the overload page

This patch uses the new sperated elastic-stores metrics for queing
delay from #123890.

Informs #121572.

Release note (ui change): The Admission Queueing Delay – Store chart
now separates elastic (background) work from the regular foreground
work.

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dbconsole: add elastic io token exhausted duration to overload page

This patch adds the metric elastic_io_tokens_exhausted_duration.kv
introduced in #124078.

Informs #121572.

Release note (ui change): The Admission IO Tokens Exhausted chart now
separates elastic and regular io work.

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Release justification: Metrics only change that will significantly help Admission Control escalations.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

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[cockroach-teamcity]

This change is