Package /data instead of userdata.img in sdk images

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 from /data by emulator.
Within the /data folder, we only keep /misc for the emulated WiFi.
This cl does not impact real devices.

BUG: 79925096

Change-Id: Ida3f2163cab30b38cd02a0280b5fd7abd9a66945
Signed-off-by: Weilun Du <wdu@google.com>
diff --git a/build/sdk.atree b/build/sdk.atree
index 4562eb5..c017600 100644
--- a/build/sdk.atree
+++ b/build/sdk.atree
@@ -231,7 +231,7 @@
 system-qemu.img                                 system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/system.img
 vendor-qemu.img                                 system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/vendor.img
 ramdisk.img                                system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/ramdisk.img
-userdata.img                               system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/userdata.img
+data/misc                                        system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/data/misc
 system/build.prop                          system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/build.prop
 
 # Note: the kernel image is handled by sdk-android-<abi>.atree now.