Fix electric-pair-skip-whitespace with quotes in text-mode

Fix electric-pair-skip-whitespace with quotes in text-mode

* lisp/elec-pair.el (electric-pair-post-self-insert-function): Don't
skip whitespace for quote syntax when `electric-pair-text-pairs'
and `electric-pair-pairs' were used.

* test/automated/electric-tests.el (electric-pair-define-test-form):
More readable test docstrings.
(whitespace-skipping-for-quotes-not-ouside)
(whitespace-skipping-for-quotes-only-inside)
(whitespace-skipping-not-without-proper-syntax):

Fixes: debbugs:17183