Enable extra flags in 'go-ts-mode' test commands

Enable extra flags in 'go-ts-mode' test commands

* lisp/progmodes/go-ts-mode.el (go-ts-mode-test-flags):
(go-ts-mode--get-test-flags): New custom variable and function
for controlling test behaviour.
(go-ts-mode--compile-test): Updated to use new test flags
variable for passing extra information to the go test command
line.
(go-ts-mode-test-this-package): Updated to use new test flags
variable for passing extra information to the go test command
line.  Removed incorrect use of -run flag.

* etc/NEWS: Announce the new user option.  (Bug#74786)

(cherry picked from commit ac3b67860761f0b80e6fd4071d1ec868a9f6b083)