Make "choice" field creation configurable

[hcw70]

I dont like the fact that sometimes
"choice" is generated as a attribute containing child elements, and sometimes it is called
"a_Or_b_Or_c" ...

I would like to have the
AttributeCompoundChoiceHandler
always emit "choice" (at least if a config option is set) instead of the "a_Or_b_Or_c" case as in

    def choose_name(self, target: Class, names: List[str]) -> str:
        reserved = set(map(get_slug, self.base_attrs(target)))
        reserved.update(map(get_slug, target.attrs))

        if len(names) > 3 or len(names) != len(set(names)):
            name = "choice"
        else:
            name = "_Or_".join(names)

        return ClassUtils.unique_name(name, reserved)

So make this something like:

    def choose_name(self, target: Class, names: List[str]) -> str:
        reserved = set(map(get_slug, self.base_attrs(target)))
        reserved.update(map(get_slug, target.attrs))

        if len(names) > 3 or len(names) != len(set(names)) or self.always_use_choice:
            name = "choice"
        else:
            name = "_Or_".join(names)

        return ClassUtils.unique_name(name, reserved)

I need to copy subtrees of xsdata instances, and so i need to fill the "choice" attribute of the parent_copy.
But if that attribute name is not constant, i ran into problems determining the container attribute of each element
separately.

[tefra]

Awesome suggestion @hcw70, the new config options are now on master

[hcw70]

Nice! Quick! and good! (as usual)!

However, dunno why you have twice "false" in
<CompoundFields defaultName="choice" forceDefaultName="false">false</CompoundFields>
...