docs: Add Disruption Schedule RFC

[jukie]

Fixes #1719

Description
This is an initial RFC designed around a draft PR I previously submitted under #1720 so that workloads can define a disruption schedule similar to NodePool Disruption Budgets.

How was this change tested?
I'm currently running a custom controller similar to https://github.com/jukie/karpenter-deprovision-controller (just a POC, don't use this) based on this design.

I've separately just discovered #2656 which may overlap a bit. @moko-poi I'd love to collaborate on something.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[k8s-ci-robot]

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This pull-request has been approved by: jukie
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[coveralls]

Pull Request Test Coverage Report for Build 20480180374

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 7 unchanged lines in 2 files lost coverage.
• Overall coverage remained the same at 80.318%

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Files with Coverage Reduction	New Missed Lines	%
pkg/controllers/provisioning/scheduling/nodeclaim.go	3	89.63%
pkg/controllers/disruption/consolidation.go	4	88.0%

Totals
Change from base Build 20440177454:	0.0%
Covered Lines:	11969
Relevant Lines:	14902

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💛 - Coveralls