feat: clear all cells

[Xazin]

Requires: https://github.com/AppFlowy-IO/AppFlowy-Collab/pull/169

Feature Preview

TBD

PR Checklist

• [ ] My code adheres to AppFlowy's Conventions
• [ ] I've listed at least one issue that this PR fixes in the description above.
• [ ] I've added a test(s) to validate changes in this PR, or this PR only contains semantic changes.
• [ ] All existing tests are passing.