docs(quota plugins): note on quotas for internal users

[PaulRMellor]

Documentation

Adds a description of the impact on internal users when applying quotas through the Kafka quotas plugin.
Describes how Topic Operator and Cruise Control operations can be affected and how to avoid any impact.

Checklist

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• Write tests
• Make sure all tests pass
• Update documentation
• Check RBAC rights for Kubernetes / OpenShift roles
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• Update CHANGELOG.md
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[pwright]

looks good, I made one dodgy suggestion, and would ask the question:
how do you monitor the situation to avoid trottling?

[fvaleri]

LGTM. Thanks.

[PaulRMellor]

Thanks for the reviews @kyguy and @scholzj
The procedure just introduces the two plugins now and keeps this info with the Kafka plugin

[scholzj]

I left one nit, but this looks reasonable to me.

[PaulRMellor]

Thanks @kyguy -- I've expanded on the potential impact to the TO operations as suggested.