patch 8.2.4723: the ModeChanged autocmd event is inefficient

Problem:    The ModeChanged autocmd event is inefficient.
Solution:   Avoid allocating memory. (closes #10134)  Rename
            trigger_modechanged() to may_trigger_modechanged().
diff --git a/src/normal.c b/src/normal.c
index e39fb77..d7a2857 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -689,7 +689,7 @@
 # endif
     }
 #endif
-    trigger_modechanged();
+    may_trigger_modechanged();
 
     // When not finishing an operator and no register name typed, reset the
     // count.
@@ -971,7 +971,7 @@
     c = finish_op;
 #endif
     finish_op = FALSE;
-    trigger_modechanged();
+    may_trigger_modechanged();
 #ifdef CURSOR_SHAPE
     // Redraw the cursor with another shape, if we were in Operator-pending
     // mode or did a replace command.
@@ -1027,7 +1027,7 @@
 	if (restart_VIsual_select == 1)
 	{
 	    VIsual_select = TRUE;
-	    trigger_modechanged();
+	    may_trigger_modechanged();
 	    showmode();
 	    restart_VIsual_select = 0;
 	    VIsual_select_reg = 0;
@@ -1151,7 +1151,7 @@
     may_clear_cmdline();
 
     adjust_cursor_eol();
-    trigger_modechanged();
+    may_trigger_modechanged();
 }
 
 /*
@@ -3222,7 +3222,7 @@
     if (VIsual_active)	// toggle Selection/Visual mode
     {
 	VIsual_select = !VIsual_select;
-	trigger_modechanged();
+	may_trigger_modechanged();
 	showmode();
     }
     else if (!checkclearop(cap->oap))
@@ -3285,7 +3285,7 @@
     if (VIsual_active && VIsual_select)
     {
 	VIsual_select = FALSE;
-	trigger_modechanged();
+	may_trigger_modechanged();
 	showmode();
 	restart_VIsual_select = 2;	// restart Select mode later
     }
@@ -5422,7 +5422,7 @@
 	{				    //	   or char/line mode
 	    VIsual_mode = cap->cmdchar;
 	    showmode();
-	    trigger_modechanged();
+	    may_trigger_modechanged();
 	}
 	redraw_curbuf_later(INVERTED);	    // update the inversion
     }
@@ -5549,7 +5549,7 @@
     foldAdjustVisual();
 #endif
 
-    trigger_modechanged();
+    may_trigger_modechanged();
     setmouse();
 #ifdef FEAT_CONCEAL
     // Check if redraw is needed after changing the state.