fix online brokers, zookeepers issues and add 2.5DC dashboard in ELK stack

[Hanxnow77]

Add AOP monitoring metrics and widgets into Kafka Overview 2.5dc dashboard, including:

• In Sync Replicas Count
• Caught Up Replicas Count
• Observers In Isr Count
• Is Not Caught Up
  Fix "Online Broker" in Kafka Overview dashboard
  Add "ZooKeeper Quorum Size" in Zookeeper Overview dashboard

[cla-assistant]

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_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[Schm1tz1]

@hifly81 - I think we want to merge this into main, not 7.2-post, right? I guess that's still related to the default branch setting for this repo.

[Schm1tz1]

Changed to main - what do you think?

[hifly81]

Changed to main - what do you think?

yes

[Schm1tz1]

LGTM

[Schm1tz1]

@Hanxnow77 - please sign the CLA. We need you to agree to it to merge the PR. Thanks!

[hifly81]

LGTM

[Schm1tz1]

Still some conflicts we need to merge manually. Maybe I can take a look tomorrow...

[hifly81]

@Hanxnow77 I can't approve it if you dont sign the CLA agreement

[Schm1tz1]

@Hanxnow77 - it's really important for us that you approve the CLA so we finally can merge your request. Please take a look and click sign if you agree, otherwise we unfortunately have to close this request.