chore(setup,cleanup): don't use Helm templates in Terraform manifests

[swiatekm]

This PR shows the entirety of the changes I want to make to our Terraform manifests used by the setup job. It is not meant to be merged - I plan to submit the changes in a series of smaller PRs. It's here so the changes can be viewed in a broader context.

There are three approaches to moving Helm templating outside Terraform manifests in this PR:

• Simple values are turned into Terraform variables. The variable values are set via environment variables, which are defined in the setup/cleanup Pod definition.
• More complex values are turned into Terraform variables, and the values are set in a templated terraform.tfvars.json file. In this file, we generate what we need by manipulating Helm dictionaries, and then convert them to JSON in one go.
• A special case of the above are source definitions. For sources, we have some maps in the configuration and want to turn them into Terraform resources. There isn't a dynamic way to do this in Terraform, so I instead decided to generate the necessary resources and local variable definitions in a sources.tf.json file. This file is then used as a reference for the actual manifests and scripts.

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[swiatekm]

Merged in #3762 #3765 #3766. #3767 remains, but it should be merged shortly. Closing.