chore: update 7.x versions

[mdelapenya]

What does this PR do?

It uses 7.x as base version everywhere.

The changes in the JSON files for testing are only replacing 8.0.0 with 7.x. In a follow-up PR, we can replace the version with the string "X.Y.Z-SNAPSHOT", and use it in the unit tests, for the sake of maintenability.

Why is it important?

Although the CI is setting the version properly (see Jenkinsfile), the local development is defaulting the values to 8.0.0-SNAPSHOT.

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 run the Unit tests for the CLI, and they are passing locally
• I have run the End-2-End tests for the suite I'm working on, and they are passing locally
• I have noticed new Go dependencies (run make notice in the proper directory)

How to test this PR locally

To run the unit tests:

make unit-tests

Related issues

• Causes by v2 refactor #1008 (the backport of the refactor did not update the versions)

Follow-ups

A PR simplifying how the version is set in tests will simplify the bump of the version in the maintenance branches. Will send it to master, applying it to all branches.

On the same hand, the very same PRs will be sent to 7.13 too: one updating the versions, one simplifying the usage.

[elasticmachine]

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Build stats

• Build Cause: Pull request #1157 opened

• Start Time: 2021-05-11T10:41:53.481+0000

• Duration: 20 min 59 sec

• Commit: b03f46e

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Test	Results
Failed	0
Passed	159
Skipped	0
Total	159

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Test stats 🧪

Test	Results
Failed	0
Passed	159
Skipped	0
Total	159