fix(jackson): replace ObjectMapper with lower-level APIs in FEEL deserializers

[chillleader]

Description

This PR replaces the temporary hotfix we had in place to fix the broken FEEL context aware deserialization.

To recap, the issue was that we are calling Jackson deserialization not only on ObjectMapper, but also on ObjectReader in case of the polling connector where we need to inject process variables into FEEL expression evaluation. We previously fetched the ObjectMapper instance from the deserialization context, but it turned out that Jackson doesn't necessarily return an ObjectMapper, but actually whatever was used to call the deserialization initially.

The proposed solution is to partially switch to lower-level APIs (such as deserializationContext.readValue(...).

• The important part was to make sure that custom modules registered with the original object reader / mapper and any custom configs will also be used in the FEEL deserializer. To check that, I added a test that requires Jackson's Java time module to be preserved in the deserializer.
• The fix also includes some refactoring of the FeelEngineWrapper for improved type cast support (moved from the deserializer) and readability.

Related issues

closes #1552