Track whether a language runtime has a supported version

In https://github.com/posit-dev/positron/pull/6934 we added some visual indicators to Python interpreters that have unsupported versions. In particular, we prepend Unsupported: to the runtimeName. This shows up whenever the full name is used.

For Python, it's technically okay for someone to use an unsupported version; there's just a chance that something won't work. So we warn the user but let them activate it anyway, just in case it's their best option.

However,

• this sometimes adds some visual clutter; if a user is using an unsupported version, the Unsupported: tag appears in the Console, Variables pane, etc. If they've gotten to that point, they probably don't care.
• this perhaps isn't visually distinct enough in the "select session" dropdown. We'd like to use an Octicon or something, but that doesn't work in the Console.

It would be nice if different UI elements could decide how to display an unsupported version differently. We could track whether it's unsupported in LanguageRuntimeMetadata.

This could be language agnostic (though arguably less useful for R).

Start by reviewing pull request 6934 and locating the LanguageRuntimeMetadata definition and its consumers. Trace where runtimeName is displayed, especially the Console, Variables pane, and session-selection dropdown. Done means unsupported status is available as separate metadata so each UI element can choose its own presentation.