Cherry-pick #23619 to 7.x: Fix refresh of monitoring configuration

[michalpristas]

Cherry-pick of PR #23619 to 7.x branch. Original message:

What does this PR do?

This PR fixes few things

1. tests for decorator were out of date

2. More sensitive monitoring change detection.
   We were only regenerating on program list change now we regenerate even on internal config change

3. Generate monitoring steps for operator not only when switch is changed but also when config is changed for agent and monitoring is running. New config will be generated and picked up by monitoring beats.

Why is it important?

Fixes: #23599

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.

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Pinging @elastic/agent (Team:Agent)

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Pinging @elastic/ingest-management (Team:Ingest Management)

[elasticmachine]

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Build stats

• Build Cause: Pull request #23636 opened

• • Start Time: 2021-01-22T10:00:03.563+0000

• Duration: 22 min 28 sec

• Commit: b010b82

Test stats 🧪

Test	Results
Failed	0
Passed	1448
Skipped	6
Total	1454

💚 Flaky test report

Tests succeeded.

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Test stats 🧪

Test	Results
Failed	0
Passed	1448
Skipped	6
Total	1454