[TM-480] Remove indigo and its subpackages

Description

Problem: we are moving indigo into a new repository, see indigo!1 (merged). So it should be removed from here.

Solution: remove the indigo package and other packages in the indigo folder. Also removed:

• website source code, mkdocs stuff, code necessary to build and upload the website;
• CI jobs: build-indigo-website, test-indigo, test-indigo-binary, test-indigo-install-script, upload-indigo-trial-image, publish-indigo-website;
• indigo part of scripts/test-docker.bats;
• indigo.sh script, installation script.

I think this MR is complete and ready for review, but we shouldn't merge it before indigo!1 (merged)

Related issue(s)

https://issues.serokell.io/issue/TM-480

✅ Checklist for your Merge Request

Related changes (conditional)

• Tests (see short guidelines)

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.

• Documentation

  • I checked whether I should update the docs and did so if necessary:
    • Root README and other README.md files
    • Haddock
    • docs/
  • I updated changelog files of all affected packages released to Hackage if my changes are externally visible.

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