Minor: Package avro dependency in connector build

[Aniket Shrimal (aniketshrimal)]

Packaging avro dependency in connector build to ensure version bump for SR dependencies is not blocked in cloud. More context - SR version bump is bringing in upgraded avro dependency (1.11.4 → 1.12.1) which is breaking the existing mongo connector.

java.lang.NoSuchMethodError: org.apache.avro.Schema$Parser.setValidate(Z)Lorg/apache/avro/Schema$Parser;
    at com.mongodb.kafka.connect.source.schema.AvroSchema.<init>(AvroSchema.java:142)
    at com.mongodb.kafka.connect.source.MongoSourceConfig.<clinit>(MongoSourceConfig.java:66)


After checking online, it looks like Avro 1.12.x has removed the setValidate(boolean) method, which explains the failure. ref: https://github.com/FasterXML/jackson-dataformats-binary/issues/514#issuecomment-2326828463

The fix we are looking to add currently is to pin the existing avro dependency version and package it in connector jar instead of using the runtime version.