This PR adds an "Unlock all" action to the edit menu.
- Selecting `unlock all` sets `isLocked` to false for all shapes on the
current page
- The option is disabled if the page is empty; but we don't check
whether there are locked shapes on the page (juice < squeeze)
Closes https://github.com/tldraw/tldraw/issues/1809
### Change Type
- [x] `minor` — New feature
### Test Plan
1. Create locked shapes
2. Select menu > edit > unlock all
### Release Notes
- Adds the unlock all feature.
af573bac51
