[zscaler_zia] Added Cloud NSS support to Zscaler ZIA package.

[vinit-chauhan]

What does this PR do?

This PR adds support of Cloud NSS to the existing Zscaler ZIA integration package. ( Cloud NSS supports DNS, Firewall, Tunnel, and Web Logs )

• Added a new data collection logic for the supported data streams.
• Added the ingest pipeline for the data stream.
• Mapped fields according to the ECS schema and added Fields metadata in the appropriate yml files
• Added dashboards and visualizations.
• Added test for pipeline for the data stream.
• Added system test cases for the data stream.

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.
• If I'm introducing a new feature, I have modified the Kibana version constraint in my package's manifest.yml file to point to the latest Elastic stack release (e.g. ^7.17.0 || ^8.0.0).

How to test this PR locally

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

elastic-package test

Screenshots

[elasticmachine]

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Build stats

• Start Time: 2022-04-26T13:00:45.002+0000

• Duration: 20 min 0 sec

Test stats 🧪

Test	Results
Failed	0
Passed	68
Skipped	0
Total	68

🤖 GitHub comments

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[andrewkroh]

I accidentally lost all my original comments so tried to recreate them rather quickly so sorry if some of them are terse. Please reach out to me if you want to discuss any of them.

[andrewkroh]

/test

[elasticmachine]

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

[vinit-chauhan]

/test

[andrewkroh]

There are some conflicts to resolve.

[vinit-chauhan]

Resolved the merge conflicts.

[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (5/5)	💚
Files	100.0% (5/5)	💚 2.941
Classes	100.0% (5/5)	💚 2.941
Methods	100.0% (66/66)	💚 12.218
Lines	94.454% (1141/1208)	👍 5.876
Conditionals	100.0% (0/0)	💚