Create emulator_* devices for emulators

aosp_arm64 has no emulators after the patch:

https://android-review.googlesource.com/c/platform/build/+/1286895

The patch creates all other emulator_* devices by cloning from
generic_*, and modify all sdk_phone_* to use them.

Bug: 111538404
Test: build sdk_phone_armv7-userdebug
Test: build sdk_phone_x86_64-userdebug
Test: build sdk_phone_x86-userdebug
Change-Id: I2b82e999ea919f005729f322cd948e6b72ba6843