Remove manual parceling from Interpolator and VolumeShaper

Created stable parcelables to hold all the data that gets parceled.
Replaced manual parceling with a two-step approach, where we first
write into the auto-generated parcelable, then parcel it.

Test: Ran audio-related CTS tests
Bug: 160253486
Change-Id: I5a4d51fb1244ed49bcd70e446aaa26e2aa8ed7b1