* lisp/progmodes/vhdl-mode.el: Use progress-reporter

* lisp/progmodes/vhdl-mode.el: Use progress-reporter

This was actually prompted by a backward compatibility problem
(because of the use of Emacs-27's `time-convert`).  The new code
seems to work fine in Emacs-25.
It also fixes a minor bug that made the echo area messages of
`vhdl-indent-region` compete with those of `indent-region`.

(vhdl-progress-info): Delete variable.
(vhdl--progress-reporter): New var to replace it.
(vhdl-update-progress-info): Delete function.
(vhdl-indent-line): Call progress-reporter-update instead.
(vhdl-indent-region): Make it an obsolete alias of `indent-region`.
Change all users.
(vhdl-align-region-groups, vhdl-align-region, vhdl-fix-case-region-1):
Use `make-progress-reporter` and `progress-reporter-update`.