Use conflict resolution dialog instead of displaying raw workspace rebase error

[mhsdesign]

The new conflict resolution is started during synchronising or publishing.
But there are further cases conflicts occur:

Resolution dialog for conflicts with base workspace on discard

Discarding a single page is only possible if there are no other conflicts with the base workspace in the workspace.

Steps to reproduce:

1. Create a conflict on PageA (492c7c86) (delete it via another user and modify PageA in your workspace)
2. Modify PageB
3. Discard only changes on PageB

Now because the content repository cannot apply the remaining changes of PageA (that were not discarded) we get a conflict.
This is currently not handled in a pretty way:

Solution could be:

Add an option to "discard selected changes AND drop conflicting changes" or "discard whole workspace"

Resolution dialog for conflicts of remaining changes in the workspace (publish and discard)

These two topics describe the problem of having an unpublishable change set:

neos/neos-development-collection#5364
neos/neos-development-collection#4997 (comment)

A simple way of creating such conflict during publish:

1. Create a PageA (5d7c9911)
2. within PageA create PageB
3. Attempt to publish only PageB

1. Create a PageA (5d7c9911)
2. within PageA create PageB
3. Attempt to discard only PageA

In #3893 we already attempted to offer a "Publish All" option that could look like this:

But there are also a lot of other variants to be respected, and we should consider offering an option to widen the selection change-set to also publish other changes based on the conflicts.