Feat: Allow specific signing for debug and release

[GMinucci]

What does this PR do

Adds the capability to specify signing for debug and/or release for each variant. This also includes a new option to allow automatic signing.

How can it be tested

Use the new properties (debug_signing and release_signing) following the provided docs and see them applied to the project once you run variants switch commad

Task

resolves #241

Checklist:

• I ran make validation locally with success
• I have not introduced new bugs
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new errors

[github-actions]

	Warnings
⚠️	Pull request is relatively big. If this PR contains multiple changes, consider splitting it into separate PRs for easier reviews.

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