D10/D9.5.x optionally support ckeditor v5 OR ckeditor v4 OR both

Problem/Motivation

D9.4/9.5/10.x offer ckeditor v5, it is installed by default on D10.x
ckeditor v4 is a contrib module now.
Due to the complexity of this upgrade and the radical api changes in ckeditor v5 (a total rewrite of ckeditor), there will be reasons why certain organisations may not be ready for ckeditor v5 but will want to use D10.x

It should be possible to enable a module like wxt_ckeditorv4 or wxt_ckeditorv5 to switch between versions, uninstall one, install the other, installing one will automatically uninstall the other. Or perhaps we may want to have both ckeditor v4 and ckeditor v5 on the same install , some content types on ckeditor v4, some on ckeditor v5 , or a toggle between versions in the node edit/node add form.

Not sure how best to approach this but thinking that a WxT D10 upgrade could be simplified by defaulting it to ckeditor v4 at first until we work out the support of ckeditor v5 with for example, Linkit, we've got an important linkit patch that I'm sure will only work with ckeditor v4 until the patch is refactored.

Steps to reproduce

TBD

Proposed resolution

TBD

Remaining tasks

TBD

User interface changes

TBD

API changes

TBD

Data model changes

TBD