Add attribtes to datalist options

for https://github.com/joomla/joomla-cms/commit/51138ffadfa55cea2652cff465aa012e025d6e22#commitcomment-6621908

The <datalist> tag and it's options  supports the Global Attributes in HTML.
then we can add class or disabled attrs to it's options.
Why we need?
an example:
country & city fields that country field is select box and city field is text input with suggestions list that user can select city from suggestions list or enter a custom city.
now we can hide or show suggestion list options with disable or enable them by jquery.


Since we only use datalists in the text formfield, I would write the code directly here either as new private method or as part of getOptions/getInput. I don't see a need for another overly complex JHtml method.
But if you must, then please do it properly with a new method. With a correct signature and without using JHtmlSelect::options (generates wrong options for datalists).