gdb-mi.el: Configure variable order and length in local-vars window

gdb-mi.el: Configure variable order and length in local-vars window

This changes allows users to configure the order of various properties
as well as truncating their length.  The full description of each
property is available as a help-text (tooltip).
* lisp/progmodes/gdb-mi.el (gdb-locals-table-row-config): New user
option.
(gdb-locals-value-filter): Don't limit the values here.
(gdb-locals-table-columns-list): New function.
(gdb-locals-handler-custom): Call it.  (Bug#59730)

* etc/NEWS: Announce the change.