[xpack][metricbeats][gcp] don't skip first value in histogram calculations

[stefans-elastic]

Proposed commit message

Don't skip first value in histogram upper bound calculations.

This should be done because according to GCP doc (https://cloud.google.com/monitoring/api/ref_v3/rpc/google.api) the histogram (Exponential and Linear) upper bound should include bucket values at index 0.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

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Author's Checklist

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How to test this PR locally

Related issues

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Screenshots

Here is screenshot from local test - values seem to be ok

Logs

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @stefans-elastic? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
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• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify]

backport-8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label and remove the backport-8.x label.

[elasticmachine]

Pinging @elastic/obs-ds-hosted-services (Team:obs-ds-hosted-services)

[ishleenk17]

@stefans-elastic : Thanks for the change.
Can we also update the sample json here.

[stefans-elastic]

@stefans-elastic : Thanks for the change. Can we also update the sample json here.

good point, thanks
updated