Add Cloudwatch Metrics Stream via PriveLink support (beta)

[daidokoro]

This PR adds support for collecting metrics using Cloudwatch Metric Streams. This solution exists only to support a specific use case, that is, send data from a cloudwatch metric stream over PrivateLink.

• initial commit
• cargo
• added metric config
• cargo fmt
• added processor code
• added metrics handler to main
• added config for metrics module
• added handler for function metrics
• initial metric test structure
• exposed metric lib
• added test dependencies
• remove unused imports
• re-add vendored openssl to fix local build
• Cargo.locl
• adjust tests
• add unit test for metrics workflow
• refactored metrics integration
• added condition to do nothing for telemetrymode metrics
• updated READEME
• add initial support for metrics workflow to cfn template
• updated template to support Cloudwatch Metrics Streams via PrivateLink
• version bump
• added initial documentation for cloudwatch metric stream workflow
• add initial concept for re-batching payload
• add drop success record
• added test fixture
• add cloudwatch metric stream workflow sequence daigram

Description

Fixes #

How Has This Been Tested?

Checklist:

• I have updated the versions in the SemanticVersion in template.yaml
• I have updated the CHANGELOG.md
• I have created necessary PR to Terraform Module Repository (https://github.com/coralogix/terraform-coralogix-aws) if needed
• This change does not affect any particular component (e.g. it's CI or docs change)