ci: remove wrapper around get charm paths and build with cache workflows

[DnPlas]

This commit removes the extra abstraction of the get-charm-paths action and build_charm.yaml reusable workflow to avoid potential incompatibilities and sync issues with the data platforms workflows.

Notes to reviewer:

• the bundle tests will be addressed in Reuse charms built with cache in bundle integration tests #654
• the on push workflow is now broken due to the changes, and it will be addressed in Use build_charm workflow from data platform in On Push workflow #650
• the release and publish workflow will be addressed in Use cached builds for release and publish workflow #656

[NohaIhab]

thanks @DnPlas, a couple comments on changes for the workflow and charmcraft versions. I suggest @carlcsaposs-canonical to also give it a review to ensure we are reusing their workflow as expected.

[mvlassis]

Very small notes.

suggestion: We could update the actions/checkout step to actions/checkout@v4 since we're updating the workflows.

[mvlassis]

Everything LGTM!