feat: Add uninstall demo/stack feature

[xeniape]

Description

Part of #187

This PR adds the uninstall subcommands to demo and stack commands. It implements the MVP features mentioned here #187 (comment)

The flag of skipping operators and CRD deletion was optional and I wasn't sure about the naming or if needs to be one command or two. Can also be just removed, added it because it was not much additional work.

Tested with all current demos/stacks. Some demos have edge cases in the deletion, will document that in the parent issue.

This PR also contains the DEMO/STACK parameter addition for stackabletech/demos#374 (comment) stripped out into #432

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

• Changes are OpenShift compatible
• CRD changes approved
• Helm chart can be installed and deployed operator works
• Integration tests passed (for non trivial changes)

Reviewer

• Code contains useful comments
• (Integration-)Test cases added
• Documentation added or updated
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added

[NickLarsenNZ]

Left a couple of comments about namespace deletion.

[Techassi]

Left a few comments and questions.