[3.14] gh-144418: Increase Android testbed emulator RAM to 4 GB (GH-148054) (#148150)

Pre-create the Android emulator image so that the the configuration can be
modified to use 4GB of RAM.
(cherry picked from commit a95ee3a21d97afdbe6bd2ce4cd8343a36cd13b02)

Co-authored-by: Malcolm Smith <smith@chaquo.com>