materialize_source_table_kafka: Include envelope_type, key_format and value_format in read func

[bobbyiliev]

Feature request

@rjobanp has added envelope, key_format, and value_format columns to the mz_internal.mz_kafka_source_tables table in this PR.

We need to extend the logic in the read function within resource_source_table_kafka.go to introduce parsing and mapping logic for the complex envelope, key, and value Terraform schema structures.

The new table values look like:

materialize=> select * from mz_internal.mz_kafka_source_tables;
  id  | topic  |      envelope_type      | key_format | value_format 
------+--------+-------------------------+------------+--------------
 u333 | topic1 | none                    |            | 
 u529 | topic1 | upsert-value-err-inline | text       | text

We need to:

1. Parse the envelope, key_format, and value_format columns from the mz_internal.mz_kafka_source_tables.
2. Map these parsed values to the appropriate Terraform schema.
3. Ensure the complex structures are accurately reflected in the resource state, especially for envelope_type, which may impact the resource behavior in Terraform.