[BUG][Kotlin] Add support for collection of generic classes (Jackson / Gson)

Created by: trietsch

Added support for collecting lists of objects for Jackson and Gson. I don't have enough knowledge about Moshi, so maybe that could be fixed by someone else in another PR. Support for Moshi added by @adamsz-lume, included in this PR.

Linked issue

[BUG][Kotlin] Generated clients cannot serialize into List<T>

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