chore: removing webhook validation in favor of kubebuilder CRD validation, and removing old SIG Gallery Logic

[Bryce-Soghigian]

Fixes #

Description
We removed ImageID from the AKSNodeClass API, and plan to add it back in the future, so i want to reduce/remove all validation in the webhooks, so removed here, and added Kubebuilder Validation instead for when we do turn it back on.

How was this change tested?
Temporarily added back in ImageID validated it validated our requests, and removed it again.

• make presubmit

Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: #
• No

Release Note

Replaced ImageID Validation webhook with CEL Validation

[Bryce-Soghigian]

/test

[Bryce-Soghigian]

Seems CI doesnt work from Fork Yet, makes sense, will reopen from branch, or can wait for it to be in place

[Bryce-Soghigian]

/test

[Bryce-Soghigian]

/test

[Bryce-Soghigian]

Seems the be lowest priority, we can close and reopen later if its needed

[coveralls]

Pull Request Test Coverage Report for Build 7967579848

Details

• -1 of 3 (66.67%) changed or added relevant lines in 2 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.05%) to 97.597%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/apis/v1alpha2/aksnodeclass_validation.go	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/apis/v1alpha2/aksnodeclass_validation.go	3	0.0%

Totals
Change from base Build 7874902941:	0.05%
Covered Lines:	35737
Relevant Lines:	36617

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💛 - Coveralls