Support deprecated packages or individual features

[teresaromero]

What does this PR do?

This PR implements support for the new deprecated field in package specifications, enabling package authors to mark entire packages or individual features (policy templates, inputs, data streams, and variables) as deprecated.

1. Added deprecated field to specifications:
   • Package-level: content and input manifest specs
   • Policy template level: integration manifest spec
   • Input level: within policy templates
   • Data stream variable level: variable definitions
2. Added deprecation as a new changelog type alongside enhancement, bugfix, and breaking-change
3. Implemented semantic validation that ensures if all inputs in an integration are deprecated, the package itself must also be marked as deprecated
4. Version compatibility: Added JSON patches to remove the deprecated field for format_version < 3.6.0

Why is it important?

This feature provides a standardized mechanism for package authors to communicate deprecation information to users, following the deprecation lifecycle defined in the RFQ

Checklist

• I have added test packages to test/packages that prove my change is effective.
• I have added an entry in spec/changelog.yml.

Related issues

• Closes Add support for new 'deprecated' field #1032

[elasticmachine]

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History

• 💔 Build #1725 failed 3e74508
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[teresaromero]

I've not included the replaced_by field, as i am not clear if this is included in the first iteration @criamico @jsoriano