Infer enum_type from default value

[bkeryan]

Problem to Solve

When specifying enum configurations, users have to specify the enum type twice: in both the default_value and enum_type parameters.

As explained in #283 (comment) , enum support uses enum_type for the annotations dictionary and uses type(parameter_metadata.default_value) when constructing enum values. This suggests that enum_type is superfluous when using the enum module (not protobuf enums).

Proposed Solution

if enum_type is None and isinstance(type(default_value), EnumMeta):
    enum_type = type(default_value)

Cc: @WesleyTangNationalInstruments

AB#2509907