patch 8.2.0970: terminal properties are not available in Vim script

Problem:    Terminal properties are not available in Vim script.
Solution:   Add the terminalprops() function.
diff --git a/src/testing.c b/src/testing.c
index c01ae3d..83e3fe4 100644
--- a/src/testing.c
+++ b/src/testing.c
@@ -854,6 +854,8 @@
 	    no_query_mouse_for_testing = val;
 	else if (STRCMP(name, (char_u *)"no_wait_return") == 0)
 	    no_wait_return = val;
+	else if (STRCMP(name, (char_u *)"term_props") == 0)
+	    reset_term_props_on_termresponse = val;
 	else if (STRCMP(name, (char_u *)"ALL") == 0)
 	{
 	    disable_char_avail_for_testing = FALSE;
@@ -861,6 +863,7 @@
 	    ignore_redraw_flag_for_testing = FALSE;
 	    nfa_fail_for_testing = FALSE;
 	    no_query_mouse_for_testing = FALSE;
+	    reset_term_props_on_termresponse = FALSE;
 	    if (save_starting >= 0)
 	    {
 		starting = save_starting;