Use aidl-defined InputChannel for parceling

Currently, InputChannel is a manually-written parcelable. In this CL, we
introduce an aidl-defined InputChannel, which eventually could also be
used in Java as well.

Now, whenever an InputChannel needs to be written to parcel, we first
create the new android.os.InputChannel and then write that object to
parcel.

Eventually, we can convert the Java side of InputChannel to use this
mechanism, as well.

Bug: 161009324
Test: adb shell monkey 1000
Test: atest libgui_test
Change-Id: Ib44c5ff02b3c77e0425b59a76195ed100e187317