purge infracost CLI command / CI jobs

[pmeier]

What does this implement/fix?

Addresses #1817 (comment).

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
• Breaking change (fix or feature that would cause existing features not to work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build related changes
• Other (please describe):

Testing

• Did you test the pull request locally?
• Did you add new tests?

Any other comments?

This is removing the nebari cost command and thus is breaking. However, this was marked "experimental"

nebari/nebari/cli/main.py

Line 420 in 4111625

[italic]This is still only experimental using Infracost under the hood.

and thus there are no BC concerns here.

[iameskild]

This looks good to me! Infracost is a neat tool but doesn't really fully capture the cost of running Nebari so it has limited utility for us and I don't think it's worth the maintenance burden.

Thanks @pmeier!