Introduce support to cloudwatch alert rule provisioning

[themarcelor]

As a follow-up of #227

This PR introduces support for Alert Rule provisioning with CloudWatch queries.

Please share your thoughts.

[codecov]

Codecov Report

Attention: Patch coverage is 89.36170% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 90.08%. Comparing base (6867a4a) to head (c54fa57).
Report is 54 commits behind head on master.

❗ Current head c54fa57 differs from pull request most recent head 4bfb6da. Consider uploading reports for the commit 4bfb6da to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #233      +/-   ##
==========================================
- Coverage   90.08%   90.08%   -0.01%     
==========================================
  Files          92       93       +1     
  Lines        6941     6988      +47     
==========================================
+ Hits         6253     6295      +42     
- Misses        543      548       +5     
  Partials      145      145              

Files	Coverage Δ
alert/queries/cloudwatch/cloudwatch.go	100.00% <100.00%> (ø)
alert/queries.go	82.75% <0.00%> (-17.25%)	⬇️

[themarcelor]

This PR is blocked by this other PR: #227

@K-Phoen please check #227 when you have a chance 🙏🏼