Limit the number of chars that can be entered in Notes custom fields displayed as TextAreas

Right now there are 2 parameters you can enter when defining new Notes custom fields displayed as TextAreas: Height (rows) and Width (columns), but these only control the size of the TextArea widget when in edit mode, not how many characters can be entered in it.

Based on end-users feedback, there is a need to limit the number of characters entered in such custom fields. We already have a 'text_length' field in the 'civicrm_custom_field' table but it currently is not used in the Notes / TextArea context (although the value 255 is inserted in the field as a default).