Add QA info to each "Ready for QA" issue

[manno]

We want to provide information for these issues, so QA can more easily test them.

The template is here: https://github.com/rancher/rancher/blob/release/v2.7/.github/pull_request_template.md

Also document, maybe in DEVELOPMENT.md?, how to handle the QA columns:

• if issue needs QA, move it to "Needs QA Review", to give them a heads up and not forget about it
• if issue is in a pre-release, move it to "Ready for QA", fill out the template, add the "zube:to-test" label

• Add QA validation request to pullrequest template #1040
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• Adds priorityClassName to deployments. #983 (done?)
• fleet-agent has high CPU usage when guest POD is in Terminating #760 (@manno)
• Fix token expiry bug #995 (@manno)