feat: Changes to Instance for day2 in API

[daniele-moro]

Description

This pull request introduces several updates to the API and internal codebase, primarily focusing on deprecating certain fields, adding new fields for runtime and OS update details, and updating validation logic. The changes aim to improve the clarity and functionality of instance resource management.

Deprecations and Replacements:

• Marked desired_os and current_os fields as deprecated in favor of OSUpdatePolicy for day2 operations and os for day0 operations. These changes are reflected in both the OpenAPI spec and protocol buffer definitions.
• Deprecated the update_status_detail field, recommending the use of OSUpdateRun instead.

New Fields for Runtime and OS Updates:

• Added runtimePackages and osUpdateAvailable fields to represent runtime package details and OS update availability, respectively. These fields are included in the OpenAPI spec, protocol buffer definitions, and documentation.

Code Adjustments:

• Added placeholders in the server logic for populating the new fields (runtimePackages and osUpdateAvailable) in the InstanceResource structure.

ITEP-67231

Any Newly Introduced Dependencies

Please describe any newly introduced 3rd party dependencies in this change. List their name, license information and how they are used in the project.

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

Checklist:

• I agree to use the APACHE-2.0 license for my code changes
• I have not introduced any 3rd party dependency changes
• I have performed a self-review of my code

The base branch was changed.

[pierventre]

I am not sure about (OPTIONAL). Either we enforce this or we remove