etags-regen-file-extensions: Enable for more extensions

etags-regen-file-extensions: Enable for more extensions

* lisp/progmodes/etags-regen.el (etags-regen-file-extensions):
Add more extensions, but remove "a".  From the ones recognized by
etags, also omit "t", "ml", "l", "def" and "inc", see
https://lists.gnu.org/archive/html/emacs-devel/2024-09/msg00735.html.
(etags-regen--all-files): Use 'string-match-p' for performance.
Bind 'case-fold-search' to t to match extensions in any case.

(cherry picked from commit 32d0c8f6af52cd8db363456d817c3d214eea4c00)