Rely on macro api in terms of conformances to make

[mikhailmaslo]

At the same time, protocols provided by macro are always empty for tests, so we have to add __testing__ tag to all sut

Before those changes macro couldn't detect such conformances

@Codable // Codable should conform only to Decodable, since Encodable is already provided by user
struct Example {
}

extension Example: Encodable { ... }

Using macro api which provides which conformances macro should generate resolve the case above