Avoid jumping too far in checkdoc-in-abbreviation-p

Avoid jumping too far in checkdoc-in-abbreviation-p

* lisp/emacs-lisp/checkdoc.el (checkdoc-in-abbreviation-p): Use
'forward-ward' instead of 'forward-sexp' to avoid jumping too far in
some situations.  (Bug#50731)

* test/lisp/emacs-lisp/checkdoc-tests.el
(checkdoc-tests--abbrev-test): New helper function.
(checkdoc-tests-in-abbrevation-p/basic-case): Rename from
'checkdoc-tests-in-abbrevation-p'.
(checkdoc-tests-in-abbrevation-p/with-parens)
(checkdoc-tests-in-abbrevation-p/with-escaped-parens): Use above new
helper function.
(checkdoc-tests-in-abbrevation-p/single-char)
(checkdoc-tests-in-abbrevation-p/with-em-dash)
(checkdoc-tests-in-abbrevation-p/incorrect-abbreviation): New tests.