Deprecate the archive store-backend

[dominiklohmann]

This removes the possibility for users to configure the archive for writing new data, and instead automatically sets the segment-store as the default store backend. Reading from the archive is still supported.

📝 Checklist

• All user-facing changes have changelog entries.
• The changes are reflected on docs.tenzir.com/vast, if necessary.
• The PR description contains instructions for the reviewer, if necessary.

🎯 Review Instructions

The change is rather local in scope, so it should be covered by CI. I recommend reviewing file-by-file.

[mavam]

Nice. I reviewed the diff and it looks sound. CI will catch the rest.