Some fixes in Cloud Foundry fields

[jsoriano]

What does this PR do?

• Remove redundant and undocumented cloudfoundry.*.timestamp fields.
• Add missing documentation about envelope fields.
• Update data.json files in metricbeat module.

Why is it important?

Avoid unnecessary duplication of data and keep documentation updated.

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.

[elasticmachine]

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

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #21175 updated]

• Start Time: 2020-09-18T18:36:15.959+0000

• Duration: 66 min 55 sec

Test stats 🧪

Test	Results
Failed	0
Passed	6518
Skipped	525
Total	7043

[ChrsMark]

In general it looks good to me! Does this need to be in sync with #21177 though?

[jsoriano]

In general it looks good to me! Does this need to be in sync with #21177 though?

Thanks! They are independent changes, but I expect conflicts yes 🙂

[jsoriano]

In general it looks good to me! Does this need to be in sync with #21177 though?

Thanks! They are independent changes, but I expect conflicts yes 🙂

I mean, they can be independently merged, but probably I will need to fix merge conflicts in one after merging the other.

[ChrsMark]

In general it looks good to me! Does this need to be in sync with #21177 though?

Thanks! They are independent changes, but I expect conflicts yes 🙂

I mean, they can be independently merged, but probably I will need to fix merge conflicts in one after merging the other.

Cool! I mostly thought about data.json file which will need to be updated in both.