Author: Bowen Fan
Author Date: 2024-04-19 05:55:27 UTC

Various minor UX improvements to account for uncommon cases

- Allow bundles to define charms with a "ch:" prefix, and remove it while parsing a bundle, if present.
- Detect if a bundle is using old Charm Store charms ("cs:" prefix), and raise an appropriate error.
- Allow bundles to use the top-level "services" key instead of "applications".
- If a track isn't given by the user on export, default to "stable" instead of "latest/stable"
  so that the Store-side default track is used.
- Account for /info response without a "readme-md" field for some charms.

Solves: https://warthogs.atlassian.net/browse/SN-2871

Merged from https://code.launchpad.net/~bowenfan/snapstore-client/+git/snapstore-client/+merge/464554