feat: Added support for self managed kafka in event source mapping

[kty1965]

Description

Resolve #277 issue.

Motivation and Context

Breaking Changes

How Has This Been Tested?

• I have tested and validated these changes using one or more of the provided examples/* projects

need to kafka brokers. you can use AWS MSK.

self_managed_kafka = {
  batch_size = 100
  starting_position = "TRIM_HORIZON"
  topics = [
    "example-topic-v1"
  ]
  self_managed_event_source = [
    {
      endpoints = {
        KAFKA_BOOTSTRAP_SERVERS = "kafka1.example.com:9092,kafka2.example.com:9092"
      }
    }
  ]
  source_access_configuration = [
    {
      type =  "SASL_SCRAM_512_AUTH",
      uri = "SECRET_AUTH_INFO"
    },
    {
      type = "VPC_SUBNET",
      uri = "subnet:subnet-example"
    },
    {
      type = "VPC_SUBNET",
      uri = "subnet:subnet-example"
    },
    {
      type = "VPC_SECURITY_GROUP",
      uri = "security_group:sg-example"
    }
  ]
}

[rollue]

Desperately in need of this PR to be merged

[antonbabenko]

This PR is included in version 3.1.0 🎉

[github-actions]

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