feat: created reusable-validate-deploy-docs workflow

[siddharth-khatsuriya]

Description

This PR removes the independent docs workflow used for managing individual add-ons and centralizes it into a unified workflow for docs validation and deployment.

Checklist

• README.md has been updated or is not required
• push trigger tests
• manual release test
• automated releases test
• pull request trigger tests
• schedule trigger tests
• workflow errors/warnings reviewed and addressed

Testing done for test-addonfactory-repo

• Manual run with deploy changes (deploy triggered only through main): https://github.com/splunk/test-addonfactory-repo/actions/runs/15205953807
• Run on push/pull_request trigger: https://github.com/splunk/test-addonfactory-repo/actions/runs/15206186580
• Blocks merge of PR if docs validation is failed and base branch is main: https://github.com/splunk/test-addonfactory-repo/actions/runs/15206262951/job/42770015163?pr=345