Use choice types for enums rather than extending enums

[hugohills-regnosys]

CDM has several usages where enums are extended, however this is not supported in Java (comparisons don't work properly)

enum EntityIdentifierTypeEnum extends PartyIdentifierTypeEnum: 
    REDID 
    CountryCode 
    Other 

enum PartyIdentifierTypeEnum: 
    BIC 
    LEI 
    MIC 

Choice types can be used as an alternative to enum extension

enum EntityIdentifierTypeEnum: <"No longer extends PartyIdentifierTypeEnum">
    REDID 
    CountryCode 
    Other 

enum PartyIdentifierTypeEnum: 
    BIC 
    LEI 
    MIC 

choice PartyOrEntityIdentifierType:
    EntityIdentifierTypeEnum
    PartyIdentifierTypeEnum

Where comparison of choice type to choice options is allowed

func IsBicOrRedId:
    inputs:
        assetIdentifier PartyOrEntityIdentifierType (0..1)
    output:
        result boolean (0..1)

    set result:
        assetIdentifier = PartyIdentifierTypeEnum -> BIC or assetIdentifier = EntityIdentifierTypeEnum -> REDID

• Comparison of choice type to choice options should be allowed for types (not just enums)
• Make the usage of enum extended a warning, and in future an error