fix: cleanup workflows and makefile

[sfc-gh-swinkler]

• changing some of the workflows and makefile to better follow convention.
• split integration.yml workflow into separate test-acceptance.yml and test-unit-and-integration.yml workflows. This should speed up by about 6 minutes
• removed the slack workflow which wasn't being used
• remove the codecov.yml file which wasn't being used
• ran make fmt to format all the terraform files and run go fumpt
• updated release.yml to use emojis

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[sfc-gh-asawicki]

This is a really hard change to be reviewed because it introduces many things we did not discuss before. It should be split into several different PRs and discussed before, so that we are all aware WHAT and WHY is being changed/introduced. Furthermore moving the package to internal was really not needed, it just messes now with all other open PRs/branches and introduces history change which makes the history of a file harder to follow.