Migrate IUsbGadget to AIDL

This change migrates android.hardware.usb.IUsbGadget to AIDL and
adds the default implementation.

Compared to the HIDL interface, AIDL based interface adds
transactionId argument to each of the interface method which
is used while invoking the corresponding callback.

Note: This is a cherry-pick of ag/16819267
Bug: 218791946
Test: USB function switch success and AIDL service is running.

Signed-off-by: Ricky Niu <rickyniu@google.com>

Merged-In: Ie05354660f13c8047e2c1712bf373e8699874d28
Change-Id: Ie05354660f13c8047e2c1712bf373e8699874d28
(cherry picked from commit 73b7652e)