Fix broken gdb-control-commands-regexp (bug#66363)

Fix broken gdb-control-commands-regexp (bug#66363)

* lisp/progmodes/gdb-mi.el (gdb-python-guile-commands-regexp):
Remove, integrate into...
(gdb-control-commands-regexp): ...this.  Translate into rx.
Remove useless submatches which broke earlier attempts at using other
submatches.  Rewrite tail expression to avoid superlinear nested
repetition, eliminating a Relint complaint.
* lisp/progmodes/gdb-mi.el (gdb-send): Simplify use of the regexp
above, and use the correct submatch this time.  Remove unnecessary and
incorrect second regexp matching.