Validate capabilityDefinitions in FindImageInCloudProfile

[Roncossek]

How to categorize this PR?

/area quality
/kind enhancement
/platform aws

What this PR does / why we need it:

Adds early validation in FindImageInCloudProfile that capabilityDefinitions is not empty. An empty slice means the caller skipped NormalizeCapabilityDefinitions(), which would cause incorrect or confusing failures downstream.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

The sibling function FindImageInWorkerStatus handles empty capabilityDefinitions via a legacy fallback. FindImageInCloudProfile has no such path, so the check makes this requirement explicit.

Release note:

Validate that `capabilityDefinitions` is not empty in `FindImageInCloudProfile` to fail fast when normalization was skipped.

[gardener-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign hebelsan for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[github-actions]

This change adds an early validation check to ensure capability definitions are not empty before processing machine images in the AWS cloud profile configuration helper function. The modification improves error handling by providing clear feedback when required capability definitions are missing and suggests using a normalization function to set defaults.

Walkthrough

• Bug Fix: Added validation to prevent processing when capability definitions are empty, providing clearer error messages and guidance for proper function usage to ensure system stability.

_{Model: claude-sonnet-4-20250514 | Prompt Tokens: 353 | Completion Tokens: 95}

[Roncossek]

cc @AndreasBurger