Upgrade emulator to emu-master-dev build 8457838 am: 7c0db0a484 am: d3507c94ad am: 293272bc72

Original change: https://android-review.googlesource.com/c/platform/prebuilts/android-emulator/+/2065607

Change-Id: Ida9d37e391e0304c66d507c9496b74ad3fea944a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>