[GCP] Add loadbalancing ingest pipeline

[ghost]

What does this PR do?

Adds loadbalancing_metrics ingest pipeline.

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.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• gcp.compute data stream does not collect data in correct namespace #4342

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• Start Time: 2022-10-04T07:47:47.526+0000

• Duration: 18 min 12 sec

Test stats 🧪

Test	Results
Failed	0
Passed	82
Skipped	0
Total	82

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🚀 Benchmarks report

Package gcp 👍(2) 💚(0) 💔(3)

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Data stream	Previous EPS	New EPS	Diff (%)	Result
dns	3021.15	1855.29	-1165.86 (-38.59%)	💔
firewall	3086.42	1968.5	-1117.92 (-36.22%)	💔
vpcflow	4694.84	2105.26	-2589.58 (-55.16%)	💔

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (5/5)	💚
Files	100.0% (5/5)	💚 2.787
Classes	100.0% (5/5)	💚 2.787
Methods	90.816% (89/98)	👍 1.134
Lines	95.752% (1375/1436)	👍 4.226
Conditionals	100.0% (0/0)	💚