Over time, we gradually deprecated the older
v1 Android embeddings based on the
io.flutter.app package.

As of Q2 2020, only 26% of applications used the v1 embeddings.

Since the v2 embeddings were strongly established over
the 7 months since the launch of Flutter v1.12,
we disabled the creation of new app and plugin
projects using the v1 embeddings.

Description of change

The flutter config command no longer has a
togglable enable-android-embedding-v2
flag (which defaulted to true since v1.12).
All projects created with flutter create
and flutter create -t plugin exclusively use the
Android v2 embedding.

Existing v1 applications continue to work.

Existing v1 applications consuming plugins now receive
a warning prompt to migrate to v2 embedding.