Revisit pmb.chroot.apk.install code

Right now, pmbootstrap is resolving all dependencies manually, and then creating a very long cmdline for apk to install all the packages, with all its dependencies.

It would be simpler to just let apk resolve the dependencies, and I'm not sure if it is still necessary to pass each and every dependency to apk beforehand. I had a reason for this when it was implemented that way, IIRC related to the feature of auto-detecting changed aports even if the pkgrel+pkgver was not changed (which we dropped, because it was not feasible). So maybe this part of the code can be simplified, let's look into this again.

(Note that we do need to resolve the dependencies beforehand, to decide if we need to build anything. But that doesn't mean that we need to tell it all to apk, instead of letting apk resolve for itself.)

Thanks to @ddevault for pointing it out in IRC recently.

EDIT: the problem of the way we do it now, is that all packages get marked as explicitly installed in apk's database after doing "pmbootstrap install". What we should have instead, is only having "postmarketos-base" and the device packages explicitly installed, and everything else pulled in as dependency.