Update Prometheus package to leverage types in remote write

[ChrsMark]

What does this PR do?

Updates Prometheus package to leverage types in remote write.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all datasets collect metrics or logs.

Related issues

• Relates Infer types in Prometheus remote_write beats#19944, Infer types in Prometheus remote_write API beats#17675

Screenshots

[elasticmachine]

Pinging @elastic/integrations-platforms (Team:Platforms)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #243 updated]

• Start Time: 2020-08-31T13:21:33.210+0000

• Duration: 3 min 26 sec

[ChrsMark]

Wondering about versioning on this https://github.com/elastic/integrations/pull/243/files#diff-7fc71a4e1d864fb27e0913069d72da8dR4. Should it be a patch upgrade or a minor number update since it introduces new functionality?

[ChrsMark]

cc: @exekias

[mtojek]

@ChrsMark I think you need to rebase this PR against the master branch.

[ChrsMark]

@mtojek the feature is implemented in Beats in 7.10 version. In this, is it ok to merge this package update now, or shall we wait? What is the process in such cases?

[mtojek]

I assume that the package-storage distribution for 7.9 has been freezed and we're safe to commit changes for 7.10. @ruflin, right?

[ruflin]

The 7.9 branch has not been created yet. But that should not hold back this PR. If the package is only compatible with 7.10, please ensure it contains the correct conditions.

[ChrsMark]

@exekias could you please have a final look on this since I applied some changes 🙂 ?