fix(codecs): support Avro Date and TimeMillis logical types - #26112

Summary

Support encoding and decoding Avro Date and TimeMillis values.
Due to the way VRL stores integers, an extra step was added to the avro encoder path to coerce Avro types based on the schema field's logical type.

References

Closes #24773

Vector configuration

sources:
  kafka_avro:
    type: kafka
    bootstrap_servers: "kafka:9092"
    group_id: "vector"
    topics:
      - test_topic
    decoding:
      codec: avro
      avro:
        schema: |
          {
            "type": "record",
            "name": "test",
            "fields": [
              {
                "name": "date_field",
                "type": { "type": "int", "logicalType": "date" }
              }
            ]
          }
        strip_schema_id_prefix: false

sinks:
  console_out:
    type: console
    inputs:
      - kafka_avro
    encoding:
      codec: json

And similar for TimeMillis.

How did you test this PR?

Manual testing with the above configs, added unit tests for coerce_logical_types and enabled the existing date/timemillis avro round trip tests. All tests passing.

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

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