Removes the remaining samples in `experimental`. They're now in the
flutter/demos repository.
*List which issues are fixed by this PR. For larger changes, raising an
issue first helps
reduce redundant work.*
#2520
## Pre-launch Checklist
- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I have added sample code updates to the [changelog].
- [x] I updated/added relevant documentation (doc comments with `///`).
* added Type Jam puzzle app for review
* pr round 2 prep
* updated ci scripts for varfont_shader_puzzle
* resolved unused and minor variable naming issues
* rotator tiles row and col are final vars now
* removed unused import and print from production
* made constructors const where needed
* pages_flow export refactored to directly come from that file
* removed old api commented out section from FragmentShaded
* updated pubspec yaml to correct project name
* dart min version updated; removed unnecessary commented out dependencies from pubspec.yaml
* updated pubspec.yaml min flutter version to ensure FragmentShader support
* added/edited comments for explanation, esp on var fonts; removed obsolete comments
* trailing newline added to pubspec.yaml eof
