prototypeItem added to ReorderableList and ReorderableListView along with tests

This reverts commit a3893aea.

Fixes https://github.com/flutter/flutter/issues/81587

The assert was never hitting because it was first hitting a
null cast error in the `renderer.parent!` line in the for
loop.

Rewrites tools/gen_keycodes, the script that generates key mappings across the framework and the engine.

a2ce3dab4 [tool] add `all` and `dry-run` flags to publish-plugin command (flutter/plugins#3776) (#81589)

This reverts commit ace61f01.

This reverts commit 027d4eca.