[integrations][Custom GCS] - Made integration GA, added new parameters & improved docs

[ShourieG]

Type of change

• Enhancement
• Documentation

Proposed commit message

• Refactored the integration.
• Added support for new GCS Input parameters according to 8.11 features.
• Updated Kibana requirements to be 8.11 and above.
• Improved the documentation to be GA ready.

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.

Note

This integration was tested manually with a real GCS bucket on cloud with 100k+ logs. Screenshot of testing is attached below.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Closes Update GCS integration to incorporate latest [GCS] input updates #8152 [Meta] Move GCS input/integration to GA #8157

Screenshots

Add here screenshots presenting:

• Test results of running GCS integration with a real GCS bucket containing 100k+ logs

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[ShourieG]

/test

[elasticmachine]

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Build stats

• Start Time: 2023-11-20T11:13:51.148+0000

• Duration: 17 min 45 sec

Test stats 🧪

Test	Results
Failed	0
Passed	3
Skipped	0
Total	3

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (0/0)	💚
Files	100.0% (0/0)	💚
Classes	100.0% (0/0)	💚
Methods	100.0% (3/3)	💚 50.0
Lines	100.0% (0/0)	💚
Conditionals	100.0% (0/0)	💚

[bhapas]

Nit

[elasticmachine]

Package google_cloud_storage - 1.0.0 containing this change is available at https://epr.elastic.co/search?package=google_cloud_storage