Fix a bug with showing the widget picker on edit activity launch.

Delaying showing the widget picker until after the edit activity has
appeared avoids an issue with transitions that results in the edit
activity being closed prematurely.

Bug: 357150334
Test: manually
Flag: EXEMPT bugfix
Change-Id: I2c7dbeb8fb330f29c72c0e6d31fa5611e6c927c2