make Py11 compliant

[SpheMakh]

• Add basetypes.EmptyClassDefault() method because dataclasses in python 3.11 cannot have mutable (classes in this case) as default values. Updated all the class defaults I could fine. It may be worth considering a

def __default__(self): 
    return dataclass.field(default_factory=self)

method to our dataclasses then using foo: Bar = Bar.__default__() when setting defaults.

• Save CASA code in a tempfile instead of parsing a multi-line code string; this did not work for me.

[o-smirnov]

One last thing @SpheMakh -- have you tried this with CASA<6 (i.e. python2 based)? Just to make sure that code still runs.

[o-smirnov]

Reminder @SpheMakh -- could you please check this implementation works with CASA5?

[SpheMakh]

Reminder @SpheMakh -- could you please check this implementation works with CASA5?

It creates even more parsing problems. But this latest solution works for CASA >=4.7, 5, and 6

[o-smirnov]

Ha, so simple in the end! All right, let's merge.

[o-smirnov]

LGTM.