Implement migration prompt to migrate from SQLite module to standalone plugin due to removal in the following release

[felixarntz]

Summary

Fixes #737

Relevant technical choices

• An admin notice is added with 3 steps to migrate, each of which is conditionally marked already completed depending where the site owner is at in the process.
• An admin pointer is added as an additional way to make site owners aware that they need to take an action, since admin notices can easily be overlooked across other admin notices.
• A few minor interoperability fixes we added (in the modules/database/sqlite files).
• No new functions are being introduced since they would need to be removed again in the following release. Therefore the new temporary code relies heavily on closures.
• Also see the requirements on the issue.

Screenshots

Admin notice awaiting step 1

Admin notice awaiting step 2

Admin notice awaiting step 3

Admin pointer

Checklist

• PR has either [Focus] or Infrastructure label.
• PR has a [Type] label.
• PR has a milestone or the no milestone label.

[mukeshpanchal27]

Thanks, @felixarntz. It looks good to me. I have some nitpick feedback and a few questions.

Sometimes, when we activate the SQLite Database Integration through step 2 and then return to the Performance Lab settings page, deactivating the module also deactivates the SQLite Database Integration plugin. is it intended behaviour?

[felixarntz]

@mukeshpanchal27

Sometimes, when we activate the SQLite Database Integration through step 2 and then return to the Performance Lab settings page, deactivating the module also deactivates the SQLite Database Integration plugin. is it intended behaviour?

I noticed that too, that's okay. It is due to the migration routine that the standalone plugin comes with. In the cases where the plugin takes care of that automatically, even better, one less step for the user.

[mukeshpanchal27]

Thanks @felixarntz, LGTM!

[felixarntz]

@aristath @joemcgill Would one of you be able to review this PR please?

[aristath]

LGTM! 👍