Fix: Angular detection in plugin loader

[jackw]

What is this feature?

I'm not entirely happy with the solution in this PR (it would probably be better to align these two different props in the backend) but this fixes a bug in production and as far as I'm aware this code will be removed when angular is also removed.

Why do we need this feature?

So angular detection occurs during plugin loading regardless of where the plugin is loaded (dashboard, datasource config page) and which backend endpoint passed the meta information to importPluginModule.

Who is this feature for?

Everybody

Which issue(s) does this PR fix?:

Fixes #

Special notes for your reviewer:

Please check that:

• [ ] It works as expected from a user's perspective.
• [ ] If this is a pre-GA feature, it is behind a feature toggle.
• [ ] The docs are updated, and if this is a notable improvement, it's added to our What's New doc.

[jackw]

This approach looks good to me! Let me know if you want me to have angular: {detected: bool} everywhere in the backend instead of angularDetected, I'm happy to help with that 🙂

Thanks for the offer @xnyo but I think we go with this for now. Like @mckn mentions it's all temporary and our time would likely be better spent elsewhere. 👍