chore: replace cloudwatch mon script with cloudwatch agent

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Issue being fixed or feature implemented

We have been using the Cloudwatch monitoring scripts written in Perl to send data from instances to Cloudwatch. These scripts seem to have been deprecated sometime in 2020, and should be replaced with Cloudwatch Agent.

What was done?

Replace unmaintained aws-scripts-mon Ansible role with maintained christiangda.amazon_cloudwatch_agent.

How Has This Been Tested?

Tested on testnet masternode-1

Breaking Changes

crontab for ubuntu user needs to be cleared and the /opt/aws-scripts-mon directory deleted on all nodes to avoid delivering metrics twice. I'll take this step when merging the PR, after verifying metrics are being delivered properly.

Checklist:

• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have added or updated relevant unit/integration/functional/e2e tests
• [x] I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• [x] I have assigned this pull request to a milestone

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Note that this will also change the namespace for shipped metrics from System/Linux to CWAgent, and also the precision/accuracy seems to change slightly too. I think this is worth it for switching to a maintained tool which delivers way more metrics than the old one. Example graph showing the jump from one namespace to another on masternode-1, compared to constantly delivered metrics on masternode-2.