Do not copy userdata.img into sdk_addon/system-image.zip

userdata.img becomes 4GB in P and it doesn't work well with patcher in
android studio. We decided to remove userdata.img in system image zip
and generate userdata.img by emulator.
This cl does not impact real devices.

BUG: 79925096

Change-Id: I5406b28291f140e2ebdbcd7c6f684f60ac59b62b
Signed-off-by: Weilun Du <wdu@google.com>