Erlang generator improvements for enum and type

[kpy3]

Another bunch of Erlang generator improvements. This time changes in type and enum generation with some minor typos.

Changes:

• Mark exception declaration with 'exception' in commentary
• Mark enum declaration with 'enum' in commentary
• Generate type for typedef declaration, use generated type instead of base type in declaration
• Generate type for enum values, type consist of declared values. Use constant names in type declaration
• Avoid integer type as enum value type, use generated type instead
• Avoid magic numbers for enum as default values, use enum's constant name instead
• Introduce nominal types (Erlang 28+)

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