ci: refactor using data platform workflows

[misohu]

Closes: #421 and #423

1. Refactors the charmcraft.yaml files to use st124 shorthand notation and python plugin instead of charm plugin for compatibility with charmcraftcache
2. Replaces the integrate.yaml and on_pull_request.yaml workflows into ci.yaml, a workflow that does the following:

• Gets the paths for the charms in the multi-charm repo
• Builds each charm in a separate runner with charmcraftcache
• Passes the built charm artifacts to test jobs
• Runs the individual integration tests for each charm
• Runs the bundle integration tests
• Publishes the built charms to <track>/edge/pr-xx channel

3. Similarly, replaces on_push.yaml with release.yaml workflow, which:

• Re-uses ci.yaml to run the builds, checks, and tests
• Published the built charms to <track>/edge only if the tests pass

4. Renames the old release.yaml to promote.yaml
5. Refactors the integration test .py files to deploy from the pre-built charms, and keeps the option for local builds

[NohaIhab]

thx @misohu, a few comments

[NohaIhab]

tiny final comments

[NohaIhab]

LGTM, thx @misohu ! Once you merge could you also send a PR to https://github.com/canonical/charmcraftcache-hub to point the branch to main? See for example canonical/charmcraftcache-hub#291