Introduce database driver extensions and autoload database drivers' dependencies

Found an issue with InstallerTestBase while working on the mysqli driver, fixed.

The test change looks good to me.
Back to RTBC.

I'm concerned about the number of low level changes we're having to make after making database drivers modules, it feels a bit like all the special casing we've had over the years for install profiles. Having said that the code here seems OK in itself. I think this should be a target for early in the 10.2.x cycle so it has time to bed in. We should resolve @quietone's recent comment though so marking needs work for that.

I have tried @quietone suggestion, but removing the line tests still fail. Reverted and reset to RTBC. Deprecations now are for 10.2.x.

Left some comments on the MR, huge effort here folks 💪

Thank for the review @larowlan! NW to go through the points.

Removed code from Database::findDriverAutoloadDirectory to use the new API. It's OK had an impact on a test. Can I get a review of latest changes before continuing with the rest of the points.

I have addressed all points from @larowlan.

All points of @larowlan have been addressed.
A couple of followups have been created.
Back to RTBC.

I took this for a spin locally, and tested that I could install with drush
Was able to install with `drush si demo_umami` and the site looked good with a click about.

I agree with @catch in #112 that its best to get this into 10.2.x early and let any issues shake out.

So in line with that, committed to 11.x - thanks all!

💃

Adjusted CR for branch, and published it.

mondrake → closed merge request !3169

I bet it's good parent 📌 [META] Improve the extension system (modules, profiles, themes) Active

Automatically closed - issue fixed for 2 weeks with no activity.

It seems like this issue caused regression on Windows: 🐛 "core_version_requirement key must be present" on core modules on Windows Needs review