[9.1] (backport #17854) adding x-metatags to openapi spec

[mergify]

Release notes

What does this PR do?

This PR updates the OpenAPI spec to add the x-metatags extension. This extension adds product_name metadata which during docs build time is converted to a meta tag on the HTML page, this tag is then parsed by our internal site search to add the API docs pages to the product facets on search.

Why is it important/What is the impact to the user?

This allows users to filter their search by logstash and only see logstash apis

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files (and/or docker env variables)
• I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

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This is an automatic backport of pull request #17854 done by [Mergify](https://mergify.com).

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[mergify]

This pull request has not been merged yet. Could you please review and merge it @georgewallace? 🙏

[mergify]

This pull request has not been merged yet. Could you please review and merge it @georgewallace? 🙏