[CQ] API: migrate FlutterSdkManager off projectOpened

[pq]

Move FlutterSdkManager (unstable) post-project open initialization to a (supported) ProjectActivity.

See: #8100, #6953

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[jwren]

This resolves the single call to projectOpened, but now we have the functionality split between two files, FlutterSdkManager and FlutterSdkManagerStartupActivity.kt, wouldn't it be more prudent to migrate the entire file over so that 1) we have one file where this logic is all shared, and 2) we don't increase the number of entries in the plugin.xml files?

With the bootstrappers, the loading in of the extensions isn't always consistent. This will potentially change the order of operations for all users or some users.

[pq]

Good questions!

I don't think we want (all of) the FlutterSdkManager registered as a startup activity and am inclined to think that checkForFlutterSdkChange should never have been in it the first place but I'm happy to discuss. (I'm not even sure it can be since it's primarily a project service.)

As for duplicate entries, even if the class were shared, it would need two entries in the xml for projectService and backgroundPostStartupActivity registrations so I don't see a way to reduce that. Or maybe you meant something else?

One thought is that we could make this a more general FlutterSdkStartupActivity so that other post startup activity logic could be hosted here too. (Another reason not to make FlutterSdkManager a ProjectActivity.)

Happy to do that when I tackle the next projectOpened migration if it sounds good to you.