[beatsauthextension] Add support for kerberos

[khushijain21]

This PR adds support for Kerberos authentication

Testing Steps:

1. Start elasticsearch with kerberos enabled.
2. Start collector with following config

receivers:
  filelog:
    include_file_name: true
    include:
      - "./otlp-all.json"

extensions:
  beatsauth:
   kerberos: 
     auth_type: "password"
     config_path: "/Users/khushijain/Documents/beats/libbeat/outputs/elasticsearch/testdata/krb5.conf"
     username: "beats"
     password: "testing"
     realm: "elastic"
    
exporters:
  debug:
    verbosity: detailed
  elasticsearch:
   endpoints:
    -  "http://elasticsearch_kerberos.elastic:9203"
   auth:
    authenticator: beatsauth
   mapping:
     mode: raw
   telemetry:
     log_response_body: true    

service:
  telemetry:
    logs:
      level: debug
  extensions: [beatsauth]
  pipelines:
    logs:
      receivers: [filelog]
      processors: []
      exporters: [debug, elasticsearch]

3. Observer no error logs
4. Observer number of documents indexed to logs-generic-default.

curl -X GET -u admin:testing "http://localhost:9203/logs-generic*/_count?pretty"
{
  "count" : 16,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  }
}

[khushijain21]

We only import beats for Kerberos config creating/validation.

There is a PR up to move kerberos package to elastic-agent-libs so that we can do not have to import beats elastic/elastic-agent-libs#360. The CI failure is also related to the same

[khushijain21]

beatsauthextension will be moved to beats. Before that a test collector distro will require to be setup in beats for easy testing. Changes from this PR will be added directly on the beats repo.

[axw]

@khushijain21 code looks fine, just one small suggestion. Can you add some tests please?

[axw]

Suggested change

	return NewKerberosClientProvider(beatAuthConfig.Kerberos, client)
	p, err := NewKerberosClientProvider(beatAuthConfig.Kerberos, client)
	if err != nil {
	return nil, fmt.Errorf("error creating Kerberos client provider: %w", err)
	}
	return p, nil

Let's wrap the error, otherwise it will be difficult to understand the "invalid authentication type" error message.

[khushijain21]

Beatsauth extension has been moved into beats codebase. The related PR to support kerberos hence is also moved there
See elastic/beats#47534