chore(demo): upgradable realm demo

[mconcat]

Added upgradable realm demo.

• admin: main entrypoint for users and controller contract for store and logic
• store: persistent storage layer across migration steps
• logic: switchable logic implementation

Contributors' checklist...

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

[dongwon8247]

It's our initial approach to tackle to the upgradable realm feature. Please have a look. @moul @zivkovicmilos @Kouteki

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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[mconcat]

Moved to manfred_upgrade_patterns folder!