[swift2objc] Support Parsing Nested Types

[nikeokoronkwo]

This issue is to track parsing of nested types (types gotten from nested structures or classes). The major instances that this issue needs to cover consist of:

• Nested types from the Self identifier (e.g when referencing an associatedType for a protocol via the symbol JSON, or in other cases)
• Basic nested structures like: String.LocalizationValue, Double.SIMD2Storage, String.UTF8View, etc.