Project tags docs

[shainaraskas]

Summary

• Creates docs for the new project tags feature, a feature that contributes to the larger cross-project search feature
• Fixes https://github.com/elastic/docs-content-internal/issues/480

Major changes:

• Documented the new project tags feature - how to create and manage tags with both the UI and the API
• Altered the overview of the project settings page to better cover the scope of what you can do with project settings
• Added a permissions requirement to the page

CAUTION: API calls in this doc are based on the TDD and have not been tested

Will possibly add some more use cases to this section as they become available if it makes sense to do so (e.g. filter projects by tag when configuring CPS)

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

2. If you answered "Yes" to the previous question, please specify the tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used:
claude 4.5 for some terminology feedback

[github-actions]

✅ Vale Linting Results

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[github-actions]

🔍 Preview links for changed docs

• deploy-manage/deploy/elastic-cloud/project-settings.md

[kilfoyle]

LGTM! ⛵

[galaxxyz]

Instructions on how to manage tags with the UI looks good to me.

I'm not sure whether all the APIs described in the document are available yet. It seems querying projects by their tags is not available.
@neethis-elastic @pugnascotia , could you help with reviewing Project tags using the {{serverless-full}} API?

[pugnascotia]

We added support for querying projects by tag in elastic/project-api#1371. Please let me know if you find any issues with it.