Fix standalone Lua script screen flicker and improve error messages (#982)

* Relax assumptions about when Lua is called in foreground and background

* Start Lua cycle timer both in foreground and background
Do not assume that background/foreground alternates

* Lua is called at every Standalone GUI cycle instead of 5 Hz
Since Lua preempts every 50 ms or so, the GUI should remain responsive.

* In standalone script, only call Lua once per GUI cycle, to avoid messing up buffer handling.

* Revamped error reporting for Standalone and Telemetry Lua scripts

* Font size for Lua error is reduced from XL to L on color if LCD_W < LCD_H

* In drawTextLines, also possible linebreaks for opening brackets.

* Smaller font for error message on tall color screen

* Make titlebar height match font size on narrow LCD

radio/src/gui/128x64/view_telemetry.cpp

@@ -170,18 +170,7 @@ bool displayTelemetryScreen()
 {
 #if defined(LUA)
   if (TELEMETRY_SCREEN_TYPE(s_frsky_view) == TELEMETRY_SCREEN_TYPE_SCRIPT) {
-    uint8_t state = isTelemetryScriptAvailable(s_frsky_view);
-    switch (state) {
-      case SCRIPT_OK:
-        return true;  // contents will be drawed by Lua Task
-      case SCRIPT_NOFILE:
-        return false;  // requested lua telemetry screen not available
-      case SCRIPT_SYNTAX_ERROR:
-      case SCRIPT_PANIC:
-        luaError(lsScripts, state, false);
-        return true;
-    }
-    return false;
+    return isTelemetryScriptAvailable(); // contents will be drawn by Lua Task
   }
 #endif
 
@@ -195,7 +184,5 @@ bool displayTelemetryScreen()
     return displayCustomTelemetryScreen(s_frsky_view);
   }
 
-
-
   return true;
 }