Move all the dependencies to their own derivation, so that we don't publish all
of them if the wrapper is installed in a profile.
The previous solution just moved them to a custom directory to avoid conflicts,
this refactors that and completely hides them, while preserving the desired
improvement of adding only one directory to each of the emacs search paths
This is to avoid unwanted side effects when installing a wrapped emacs in the environment:
* All executables in the dependencies become available in the user environment
* All site-lisp binaries in the dependencies become accessible to unwrapped emacs
Also, both bin and site-lisp would generate conflicts so installing a wrapped emacs becomes really cumbersome
Fixes#10819. emacsWithPackages will know its own package set. This
requires it to be in a package set, rather than at the top level, so it
lives in emacsPackagesNg.
Emacs will call package-initialize itself, if required, or the user will
call it in their initialization file. There is no reason to call it in
the wrapper and doing so only increases start-up time.
