[Cassandra] Update as per best practices

[harnish-crest]

• Enhancement

What does this PR do?

This PR enhances the Cassandra integration with some of the best practices of developing integration packages.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

How to test this PR locally

• Clone integrations repo.
• Install elastic-package locally.
• Start elastic stack using elastic-package.
• Move to integrations/packages/couchbase directory.
• Run the following command to run tests.

elastic-package test

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2022-08-17T05:18:35.434+0000

• Duration: 17 min 27 sec

Test stats 🧪

Test	Results
Failed	0
Passed	12
Skipped	0
Total	12

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

[kush-elastic]

/test

[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (1/1)	💚 2.913
Classes	100.0% (1/1)	💚 2.913
Methods	100.0% (13/13)	💚 10.3
Lines	91.228% (52/57)	👎 -0.515
Conditionals	100.0% (0/0)	💚

[kush-elastic]

LGTM