This PR fixes several bugs related to live tests, adds more tests, and completes the documentation of several methods related to pointer events.

e193daf1e [camera] Add `CameraOptions` used to constrain the camera audio and video (flutter/plugins#4164) (#86673)

Some embeddings might send pointer events with buttons = 0x2 (right-click) for touch or stylus device kinds. If the primary button is synthesized for those events, they won't behave properly. Without this change it's not possible to trigger "secondary tap" events on a TapGestureRecognizer while using a stylus or on an iPad trackpad, since that recognizer will receive buttons = 0x3.

Disable the automatic "pub get" if the project is using a third-party tool for linking dependencies. (#86177)

* add a check for env variable RELEASE_CHANNEL in dev/snippets/lib/main.dart during doc generation
* update to LUCI_BRANCH, which is already populated
* validate env variable is either master or stable

When suggesting more performant alternatives to rebuilding `Opacity`, `FadeTransition` is as valid as `AnimatedOpacity`, and it's less obvious ("opacity" versus "fade").

f726c319a [camera] Fix coordinate rotation for setting focus- and exposure points on iOS (flutter/plugins#4158) (#86542)

This reverts commit a67f618a.