patch 8.2.2638: cannot write a message to the terminal from the GUI

Problem:    Cannot write a message to the terminal from the GUI.
Solution:   Add :echoconsole and use it in the test runner. (issue #7975)
diff --git a/src/eval.c b/src/eval.c
index 6cdc10f..95dd5e2 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -6117,6 +6117,7 @@
  * ":execute expr1 ..."	execute the result of an expression.
  * ":echomsg expr1 ..."	Print a message
  * ":echoerr expr1 ..."	Print an error
+ * ":echoconsole expr1 ..." Print a message on stdout
  * Each gets spaces around each argument and a newline at the end for
  * echo commands
  */
@@ -6194,6 +6195,11 @@
 	    msg_attr(ga.ga_data, echo_attr);
 	    out_flush();
 	}
+	else if (eap->cmdidx == CMD_echoconsole)
+	{
+	    ui_write(ga.ga_data, (int)STRLEN(ga.ga_data), TRUE);
+	    ui_write((char_u *)"\r\n", 2, TRUE);
+	}
 	else if (eap->cmdidx == CMD_echoerr)
 	{
 	    int		save_did_emsg = did_emsg;