feat(examples): finalize acl package

[0xtekgrinder]

This PR adds missing functionalities from the acl package:

• helpers to remove permissions.
• helpers to adds multiple permissions at once -> {verbs: []string{"read","write"}}.
• helpers to delete users from groups.
• helpers to quickly reset states.

Everything can be tested by running gno test examples/gno.land/p/demo/acl

Contributors' checklist...

• [X] Added new tests, or not needed, or not feasible
• [X] Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• [X] Updated the official documentation or not needed
• [X] No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• [ ] Added references to related issues and PRs
• [X] Provided any useful hints for running manual tests