Cherry-pick #19018 to 7.x: Add basic cloudfoundry integration tests

[jsoriano]

Cherry-pick of PR #19018 to 7.x branch. Original message:

What does this PR do?

Add some basic integration tests for cloudfoundry.

By now these tests follow the approach we are following with cloud features, they need a cloud foundry deployment whose configuration is provided using environment variables, and tests are only executed if some tag is set. So they are not going to be executed in CI by now.

Instructions to have a working cloud foundry deployment will be added in a future PR.

Why is it important?

To have some integration tests as reference before starting with further refactors.

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 Instructions to have a cloud foundry deployment for development will be added in a future PR.
• 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.

How to test this PR locally

export CLOUDFOUNDRY_API_ADDRESS=...
export CLOUDFOUNDRY_CLIENT_ID=...
export CLOUDFOUNDRY_CLIENT_SECRET=...
go test -tags=integration,cloudfoundry ./x-pack/filebeat/input/cloudfoundry/ ./x-pack/metricbeat/module/cloudfoundry/...

Related issues

• Part of elastic/beats#17539

[elasticmachine]

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

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #19160 opened]

• Start Time: 2020-06-12T15:06:51.595+0000

• Duration: 51 min 37 sec

Test stats 🧪

Test	Results
Failed	0
Passed	2795
Skipped	340
Total	3135