Fix #8924 - Speed up rendering of the script list

[kkthxbye-code]

Fixes: #8924

Loading the script list can become slow when having multiple large scripts. The reason is that django instantiates the Script class for each access in the template. This can be very slow in some cases.

The fix is simply to set do_not_call_in_templates = True on the callable before passing them to the template. Please let me know if there is a better option.

The template was changed slightly, as the script variable did not return the name when not instantiated. Name is now taken from Meta instead.

[kkthxbye-code]

@jeremystretch - I moved do_not_call_in_templates to the base class.

I also changed the template to use script.name. I had to change it from self.__class__.__name__ to self.__name__. I tested on our production system (v3.1.5) and if you omit Meta.name the name of the script will be "type" (metaclass of new-style classes). I might be missing how it's supposed to work, but I think that's a bug.