refactor: always have a dependency against COSI for kubecost

[takirala]

What problem does this PR solve?:

Follow up of #2959

Refactors the kubecost manifest to always depend on cosi. Adds a dashboard CM as well as some code cleanup.

Which issue(s) does this PR fix?:

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Checklist

• If the PR adds a version bump, ensure there is no breaking change in Licensing model (or NA).
• If a chart is changed or app configuration is significantly changed, the chart version is correctly incremented (so that apps are not automatically upgraded from a previous version of DKP).

[coveralls]

Pull Request Test Coverage Report for Build 12701060373

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 51.703%

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Totals
Change from base Build 12675253962:	0.0%
Covered Lines:	167
Relevant Lines:	323

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💛 - Coveralls