Improve PredefinedExpressions and add Python dict to Mathics3 Association conversion

[rocky]

• Add a way that from_python() can convert a dictionary to an Association.
• Remove ExpressionInfinity. This is a duplicate of MATHICS3_INFINITY.
• Fill in more properties for predefined constants; set Python and SymPy corresponding values
• Define ELEMENTS_FULLY_EVALUATED for use on fully-evaluated constants.

[mmatera]

OK, this does not seem to have any to do with Association, but looks good.

[mmatera]

LGTM

[rocky]

OK, this does not seem to have any to do with Association, but looks good.

The association with Association:

def association_from_dict(arg: dict, options: ToPythonOptions) -> BaseElement:
    from mathics.core.expression import Expression

    entries = [
        Expression(
            SymbolRule,
            from_python(key, options),
            from_python(value, options),
        )
        for key, value in arg.items()
    ]
    return Expression(SymbolAssociation, *entries)

This will be used by Import of a ZIP file in showing Summary items. For example:

In[1]:= Import["t1.zip", "Elements"]                                                    
Out[1]= {FileNames, Summary}

In[2]:= Import["t1.zip", "Summary"]                                                     
Out[2]= Dataset[<|Format -> ZIP, FileName -> t1.zip, FileSize -> 5.675 kilobytes|>, 
 >    TypeSystem`Struct[{Format, FileName, FileSize}, 
 >     {TypeSystem`Atom[String], TypeSystem`Atom[String], TypeSystem`Atom[1 kilobyte]}]\
 >     , <||>]