Add docker image generation and sigv4 roleArn support

[bitkill]

Description of changes:

• Add ghcr docker image for CWMetricStreamExporter
• Add support for a alternative role to call AMP (useful in the case of cross-account IAM roles)
• Add .gitignore to the lambda folder.
• Move .github folder to root, to be able to run the actions
• Update dependencies to the most recent version
• Add support for multiple dimensions by using a map instead of a struct

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[bitkill]

Hi @rmcdonough , can you have a look at this? I don't know who manages these repos, but I'm pretty sure no one is notified without a CODEOWNERS file. Thanks!

[rmcdonough]

Hi @rmcdonough , can you have a look at this? I don't know who manages these repos, but I'm pretty sure no one is notified without a CODEOWNERS file. Thanks!

That should be take care of now ;)