fix: Replace the channel input with risk

[MichaelThamm]

Issue

Since we need to move to workload tracks for charms, our product component (the charm TF modules) tracks will no longer be in sync. This means that the channel input is no longer useful in products and we really only care about risk.

Blocked by:

• fix: Remove the TF channel input validation #274

Solution

We can hardcode the tracks of the components e.g., 0.31 for alertmanager and 3.10 for prometheus in the module TF tag 3.0.n. The user should not have to concern themselves with what track of COS they want because this has caused confusion in the past i.e., the reason we added channel input validation, which is simplified if we only expose a risk.

Checklist

• I have added or updated relevant documentation.
• PR title makes an appropriate release note and follows conventional commits syntax.
• Merge target is the correct branch, and relevant tandem backport PRs opened.

Context

Keeping the channel input maintains backwards compatibility with COS < 3 so users have easier adoption, but this is giving users a false impression that they can choose a track with this input, but they cannot.

Testing Instructions

Upgrade Notes

[MichaelThamm]

Closing this PR in favor of:

• feat: juju_charm datasource and a upgrades.tf file #278