This adds a post-process step which automatically adds unambiguous imports,
removes unused imports and sorts the import list (formatting matches standard
IntelliJ settings).
This will preserve line count across versions at all cost.

Java only for now because it's a lot more tricky with Kotlin and we don't yet
use Kotlin ourselves (and won't be preprocessing it in the future either).

In these cases, the getMethod of the property will not have a Psi element and we
need to traverse up the overrides until we find one that does.

While one might at first think that multiple changes should conflict if they
target that same start point, that is not necessarily true as long as no more
than one of them includes deletions: There may be an arbitrary number of
insertions at the same position (regular remapping never just inserts but
patterns can).

When we used to remap `a.pkg.A.Inner` we would apply both mappings (the one for
the inner class and the one for the outer class) at the same time, resulting in
`b.pkg.B.Inner.Inner`.
The direct cause being that we only checked conflicts for the range of the
respective expression (which is just `A` and `Inner` for Kotlin, and therefore
not conflicting) instead of the parent as we should have.

With that fixed, it now also becomes apparent that we need to apply mappings for
dot qualified expressions back to front (otherwise the outer class takes
priority), so that is the second thing this commit change.