patch 8.2.4157: terminal test fails because Windows sets the title

Problem:    Terminal test fails because Windows sets the title.
Solution:   Add the "vterm_title" testing override and use it in the test.
            (Ozaki Kiichi, closes #9556)
diff --git a/src/testing.c b/src/testing.c
index 3482682..4d2a942 100644
--- a/src/testing.c
+++ b/src/testing.c
@@ -1053,6 +1053,8 @@
 	    ui_delay_for_testing = val;
 	else if (STRCMP(name, (char_u *)"term_props") == 0)
 	    reset_term_props_on_termresponse = val;
+	else if (STRCMP(name, (char_u *)"vterm_title") == 0)
+	    disable_vterm_title_for_testing = val;
 	else if (STRCMP(name, (char_u *)"uptime") == 0)
 	    override_sysinfo_uptime = val;
 	else if (STRCMP(name, (char_u *)"autoload") == 0)