fixes [Additional color mappings for FAB in Material 3](https://github.com/flutter/flutter/issues/130702)

### Preview
![image](https://github.com/flutter/flutter/assets/48603081/a6f9aef6-af80-41ce-8e59-50f095db047d)

Migrate tests in flutter/flutter. Once the tests here and in `*_customer_testing` are migrated, the default value of the migration flag will be changed from false to true, making the rounding hack disabled by default.

Of the original 4 examples, the first 3 mostly covered the same API features and occupied quite a bit of real-estate at the top of https://api.flutter.dev/flutter/material/FloatingActionButton-class.html.  Additionally the illustrations and the code samples didn't match in some cases.

Replaced examples 0,1,2 with one example that changes attributes of the FAB when it's pushed. 

Fixes https://github.com/flutter/flutter/issues/128048

Rename Sample classes