[GCP] Add missing cloud.provider field to GCP datastreams

[legoguy1000]

What does this PR do?

Add missing cloud.provider field to GCP datastreams

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

• Closes [GCP] Log collection integrations does not set cloud.provider #3270

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• Start Time: 2022-05-05T16:24:12.681+0000

• Duration: 18 min 40 sec

Test stats 🧪

Test	Results
Failed	0
Passed	24
Skipped	0
Total	24

🤖 GitHub comments

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[efd6]

LGTM after version fix.

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

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (4/4)	💚
Files	100.0% (4/4)	💚 3.623
Classes	100.0% (4/4)	💚 3.623
Methods	100.0% (54/54)	💚 11.716
Lines	96.213% (1118/1162)	👍 7.293
Conditionals	100.0% (0/0)	💚