Replace Jackson with kotlinx.serialization

[ArtificialPB]

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📝 Description

Migrate to kotlinx.serialization, which supports kotlin multiplatform.

Use json-okio module in HttpClient to write content directly to request body. It might also make sense to consider implementing custom JsonWriter which supports serializing directly to ByteArray, instead of converting first to String. See: https://github.com/Kotlin/kotlinx.serialization/blob/master/formats/json-okio/commonMain/src/kotlinx/serialization/json/okio/internal/OkioJsonStreams.kt#L37

Implement custom serializers and deserializers for common types: Address, Bytes, Hash, Bloom, Long (hex), Int (hex), BigInteger (hex). Covering the low-level types with custom serializers will make it easier to implement the top-level ones, e.g. RPCTransaction. If the performance is not good enough with compiler-generated top-level type serializers, implement custom serializers also for them.

Serializers: https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md