Android v1 embedding app and plugin creation deprecation

Summary

Context

Description of change

Migration guide

Timeline

Summary

The flutter create templates for apps and plugins
no longer create Android wrapping based on the
v1 Android embedding as part of our gradual
Android v1 embedding deprecation process described in our
Android Migration Summary.

Application projects using the v1 Android embedding
are encouraged to migrate following the steps described in
Upgrading pre 1.12 Android projects.

Plugins targeting the v1 Android embedding are encouraged
to migrate following the instructions in
Supporting the new Android plugins APIs.

Context

In Flutter version 1.12, we launched a v2 set of
Android APIs based on the io.flutter.embedding
package in order to enable the add-to-app workflow
on Android.