Add offload_support flag to aaudio.aconfig

This flag will be used to enable offload support in AAudio.

Bug: 372041799
Test: TH
Flag: com.android.media.aaudio.offload_support
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:c3e3eced45ce32111a9e873875383ffc4f86feae)
Merged-In: Ic14adea7a896409d4d967c54725595f77f32cb91
Change-Id: Ic14adea7a896409d4d967c54725595f77f32cb91