This change:

* Adds a boolean to `multiViewEnabled`.
* Removes unused `canvasKitMaximumSurfaces` value.

Part of: https://github.com/flutter/flutter/issues/137377

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style