Add Jammy stack to .NET 6 dependencies

[fg-j]

Summary

The Paketo Jammy Stacks RFC has been accepted, and specifies that the Jammy Full and Base stacks will have the stack ID io.buildpacks.stacks.jammy. .NET 3.1 does not work on Jammy Jellyfish because it requires an outdated version of OpenSSL. So, this PR adds the Jammy stack only to the .NET 6 dependencies.

A related dep-server PR will honor this change for new versions of .NET as they're added. Once this is approved, I'll also updated the existing metadata.json for the dependencies currently in the buildpack to reflect this change.

Use Cases

Will allow the .NET Core buildpack to run on Jammy.

Checklist

• I have viewed, signed, and submitted the Contributor License Agreement.
• I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• I have added an integration test, if necessary.
• I have reviewed the styleguide for guidance on my code quality.
• I'm happy with the commit history on this PR (I have rebased/squashed as needed).

[fg-j]

@sophiewigmore I'm thinking that the easiest way to change the metadata in the dep-server at this point is to go in, remove the .NET 6 versions in the buildpack (6.0.5 and 6.0.6) from the "known versions" list, and then let the dep server update the metadata automatically. Does that seem reasonable?

[fg-j]

I've updated the known-versions file. Metadata updates in the dep server should be making their way through shortly.

[fg-j]

See #353 for stack list updates