[DOCS] Enhance troubleshooting high cpu page. Opster migration

[thekofimensah]

This is importing additional information given in the Opster docs for high cpu issues.

Summary of changes:

1. Moved the “Hotspotting” paragraph at the beginning into the “Tips and Solutions” section for better contextual fit, incorporating extra details from the Opster documentation.
2. Added new subsections to “Tips and Solutions,” specifically covering JVM garbage collection and oversharding.
3. Separated the previous three points (“Scale your cluster,” “Spread out bulk requests,” and “Cancel long-running searches”) into a distinct section, as they are less common scenarios and more general best practices rather than direct solutions to typical high CPU issues.

This is the backport: elastic/elasticsearch#125558

[thekofimensah]

@leemthompo I'm still getting this issue where the md redirect goes to the middle of the page. I think wherever the link is in the original page, it is automatically scrolled to that same place in the new page.

It would be great if you can check the "hot spotting" or "data tier" link and if it's not just me, I can create a ticket

[thekofimensah]

@georgewallace

[thekofimensah]

@shainaraskas , I made the changes to the headings, not sure if "check-cpu-usage" for example needs to be more unique to this page, or not.

Also i rewrote the oversharding paragraph to remove that first sentence but also realized I needed to clarify it a bit

[shainaraskas]

I think this is ok to go now, but I provided a couple of suggestions we could address while we're here

[shainaraskas]

these should be sentence case

Suggested change

	| GC Type | Completion Time | Occurrence Frequency |
	| GC type | Completion time | Frequency |

[shainaraskas]

looking at this section, the first 3 items are not CPU usage reduction recommendations.

what would you think about breaking the section into "Common causes of high CPU usage" and "Reduce high CPU usage" so one has links to additional problem spaces and one has general recommendations?

[shainaraskas]

Suggested change

	Oversharding occurs when a cluster has too many shards, often times caused by shards being smaller than optimal. While Elasticsearch doesn’t have a strict minimum shard size, an excessive number of small shards can negatively impact performance. Each shard consumes cluster resources since Elasticsearch must maintain metadata and manage shard states across all nodes.
	Oversharding occurs when a cluster has too many shards, often times caused by shards being smaller than optimal. While {{es}} doesn’t have a strict minimum shard size, an excessive number of small shards can negatively impact performance. Each shard consumes cluster resources because {{es}} must maintain metadata and manage shard states across all nodes.