fix: temp exclude SKUs without compatible VM image

[tallaxes]

Fixes #616

Description

Exclude from consideration VM SKUs that don't have a compatible (= tagged for NVMe) VM image in community image galleries - for now, until the VM images are properly tagged. The implementation only allows VM SKUs that support SCSI (defined as either declaring SCSI support in their DiskControllerType, or not declaring anything at all).

Possible alternative implementations (which we may consider in the future):

• Internally assign corresponding capabilities (e.g. karpenter.azure.com/controller-disk-type) to both instance types (derived from VM SKUs) and images (either statically or derived from image definition) and rely on requirements compatibility, and dynamically take VM SKUs without compatible image support out of consideration. This would have a side benefit of being able to select controller-disk-type.
• Detect persistent / non-retriable failure to provision certain VM SKUs and take them out of consideration.
• Use explicit VM SKU allowlist

How was this change tested?

• make presubmit
• local testing with Fv6
• E2E test: https://github.com/Azure/karpenter-provider-azure/actions/runs/12307523172 (passed)

Does this change impact docs?

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

Release Note

Exclude from consideration VM SKUs that don't have a compatible (= tagged for NVMe) VM image

[coveralls]

Pull Request Test Coverage Report for Build 12307396129

Details

• 240 of 240 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 94.257%

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Totals
Change from base Build 12167425051:	0.03%
Covered Lines:	37354
Relevant Lines:	39630

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💛 - Coveralls

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Files not reviewed (1)

• hack/codegen.sh: Language not supported

Comments suppressed due to low confidence (2)

pkg/providers/instancetype/instancetypes.go:278

• [nitpick] The variable name 'useSIG' is ambiguous. It should be renamed to 'useSharedImageGallery' for better clarity.

useSIG := false // replace with options.FromContext(ctx).UseSIG when available

pkg/providers/instancetype/instancetypes.go:413

• The function 'isCompatibleImageAvailable' should have test coverage to ensure its correctness.

func isCompatibleImageAvailable(sku *skewer.SKU, useSIG bool) bool {