Kafka sasl mechanism

[lalit-satapathy]

What does this PR do?

kafka integration will be passing down sasl.mechanism for consumergroup & partition data_streams.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have added an entry to my package's changelog.yml file.

Author's Checklist

• Review Kafka metricbeat yml for sasl mechanism input

How to test this PR locally

• Verify that the config is populated in the generated policy file.
• No Kafka system test for now.

Related issues

• Closes kafka integration not using sasl.mechanism for consumergroup & partition data_stream #3667

Screenshots

      - id: kafka/metrics-kafka.partition-2b7de019-5e65-4fc2-a011-2e80100604bf
        data_stream:
          dataset: kafka.partition
          type: metrics
        metricsets:
          - partition
        period: 10s
        hosts:
          - 'localhost:9092'
        username: u1
        password: p1
        sasl.mechanism: SCRAM-SHA-256

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Build stats

• Start Time: 2022-09-07T13:20:47.676+0000

• Duration: 14 min 39 sec

Test stats 🧪

Test	Results
Failed	0
Passed	31
Skipped	0
Total	31

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (1/1)	💚 2.814
Classes	100.0% (1/1)	💚 2.814
Methods	72.222% (13/18)	👎 -17.202
Lines	77.778% (56/72)	👎 -13.174
Conditionals	100.0% (0/0)	💚

[ManojS-shetty]

LGTM!