patch 9.0.0683: cannot specify a time for :echowindow

Problem:    Cannot specify a time for :echowindow.
Solution:   A count can be used to specify the display time. Add
            popup_findecho().
diff --git a/src/vim9instr.c b/src/vim9instr.c
index 18dad11..4407d59 100644
--- a/src/vim9instr.c
+++ b/src/vim9instr.c
@@ -1879,7 +1879,21 @@
     if ((isn = generate_instr_drop(cctx, isn_type, count)) == NULL)
 	return FAIL;
     isn->isn_arg.number = count;
+    return OK;
+}
 
+/*
+ * Generate an ISN_ECHOWINDOW instruction
+ */
+    int
+generate_ECHOWINDOW(cctx_T *cctx, int count, long time)
+{
+    isn_T	*isn;
+
+    if ((isn = generate_instr_drop(cctx, ISN_ECHOWINDOW, count)) == NULL)
+	return FAIL;
+    isn->isn_arg.echowin.ewin_count = count;
+    isn->isn_arg.echowin.ewin_time = time;
     return OK;
 }