Before layers were sometimes only activating the non strict
version of smartparens. Also some were only disabling
the non-strict version leaving some of the smartparens
advices intact.
With this PR, all layers set the right version of smartparens.
Also if the layer is trying to disable it a standard function
will now take care to disable all versions of smartparens.
This reverts commit 29c78ce841 and all other fixes
that have been made afterwards.
The motivation is that use-package is seen by many as a replacement for
`require`. Is use-package always defer the loading of packages then is breaks
this use case, this does not respect POLA so even if it was making Spacemacs
loading faster (up to 3s faster on some startup on my machine) we just cannot
use it, it would be irresponsible. Spacemacs should be easy to use, loading
performance will come with time but it is not a priority.