Allow enabling smarty escape by default with Smarty5

[eileenmcnaughton]

This makes Smarty5 respect the constant CIVICRM_SMARTY_DEFAULT_ESCAPE - this was something we were close to getting viable with Smarty2 but put on hold in order to work on updating smarty. It is not an option for Smarty3 & 4 & has no production usage in 2 but with this it can be enabled on 5 & with civicrm/civicrm-core#30566 it loads without crashing

civicrm/civicrm-core#30567 & a larger one doing the same thing are required to get it to not have UI issues

I kept the class in packages as the main Smarty class is currently there to avoid conflict & it feels sane to keep it together - at some point we would move it to \Civi\Smarty5\ I think but we need to cull smarty versions first

[civibot]

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