Feature/nginx ingress controller ipv6

[gsantoro]

What does this PR do?

• Handle multiple upstream servers
• Handle [] around IPv6 in upstream servers addresses

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

• All pipeline tests are passing

How to test this PR locally

• run elastic-package test pipeline -v from inside the nginx_ingress_controller package

Related issues

• Closes IPv6 address is not correctly parsed in nginx_ingress_controller integrations #4128

[elasticmachine]

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Build stats

• Start Time: 2022-09-07T09:49:27.057+0000

• Duration: 15 min 11 sec

Test stats 🧪

Test	Results
Failed	0
Passed	30
Skipped	0
Total	30

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (2/2)	💚 2.814
Classes	100.0% (2/2)	💚 2.814
Methods	100.0% (25/25)	💚 10.637
Lines	93.769% (316/337)	👍 2.442
Conditionals	100.0% (0/0)	💚