BP: Rewrite built-in processors

[lovromazgon]

• Implement new list of processors defined in the design document
• Make sure each processor is documented and uses the specification generator to extract the specification from Go docs
• Full list:
  • [ ] field.set - set a field in the record https://github.com/ConduitIO/conduit/pull/1371
  • [ ] field.subset.exclude - remove fields from the record if they are on the list https://github.com/ConduitIO/conduit/pull/1371
  • [ ] field.subset.include - remove fields from the record if they are not on the list
  • [ ] field.rename - rename fields https://github.com/ConduitIO/conduit/pull/1371
  • [ ] field.convert - convert one type into another in a structured payload https://github.com/ConduitIO/conduit/pull/1371
  • [ ] filter - ack record and remove it from the pipeline https://github.com/ConduitIO/conduit/pull/1371
  • [ ] decode.avro - decode Avro data into structured data
  • [ ] decode.json - decode a JSON string into structured data
  • [ ] encode.avro - encode structured data into Avro data
  • [ ] encode.json - encode structured data into a JSON string
  • [ ] unwrap.kafkaconnect - unwrap a Kafka Connect payload into the current record
  • [ ] unwrap.debezium - unwrap a Debezium payload into the current record #1393
  • [ ] unwrap.opencdc - unwrap a OpenCDC payload into the current record #1387
  • [ ] webhook.http - send a HTTP request for each record #1382
  • [ ] custom.javascript - execute JavaScript code for each record https://github.com/ConduitIO/conduit/pull/1374

[maha-hajja]

design doc https://github.com/ConduitIO/conduit/blob/main/docs/design-documents/20231117-better-processors.md