I previously made a PR (#136140) that used `switch` expressions to make some parts of the Flutter codebase easier to understand. It was assigned to the framework team, and @christopherfujino let me know that it was too large to effectively review and recommended breaking it up into smaller pull requests.

Here's a PR that only targets files in the `dev/` directory. Hopefully this will be easier to work with!

(solves issue https://github.com/flutter/flutter/issues/136139)

Remove 1745 decorative breaks

This reverts commit 5fd259be.

update hot reload benchmark to be more representative

This reverts commit 7ba775a9.

Move Flutter Gallery to dev/integration_tests/ as it is an older copy used only for testing. The current version of the Flutter Gallery now lives in https://github.com/flutter/gallery.