refactor: split `AbstractJsonLdTransformer` into 2 different collaborators

# Feature Request

`AbstractJsonLdTransformer` has become too much to handle, it avoids some duplication but it does not provide abstract features that could make the json-ld transformation easier. Actual transformers are still not easy to test.

My proposal would be to have 2 different services:
- `JsonLdSerializer` (to be used in the `JsonObjectFrom...Transformer`s)
- `JsonLdDeserializer` (to be used in the `JsonObjectTo...Transformer`s)

that will be user

## Which Areas Would Be Affected?

_e.g., DPF, CI, build, transfer, etc._

## Why Is the Feature Desired?

_Are there any requirements?_

## Who will sponsor this feature?

_Please @-mention the committer that will sponsor your feature_.

## Solution Proposal

_If possible, provide a (brief!) solution proposal._