Remove network and diskio metrics from ec2 metricset

[kaiyan-sheng]

What does this PR do?

With #13203, rate metrics are calculated based on network and diskio metrics. With the new rate metrics, original metrics can be removed in 8.0.0. The default ec2 dashboard need to be changed as well.

closes #13359

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.

[mergify]

This pull request does not have a backport label. Could you fix it @kaiyan-sheng? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[elasticmachine]

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Build stats

• Start Time: 2021-10-19T13:58:46.161+0000

• Duration: 80 min 19 sec

• Commit: 7de8b83

Test stats 🧪

Test	Results
Failed	0
Passed	2666
Skipped	248
Total	2914

💚 Flaky test report

Tests succeeded.

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[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b remove_fields_ec2 upstream/remove_fields_ec2
git merge upstream/master
git push upstream remove_fields_ec2