Use __ANDROID_VENDOR_API__ for vendor API surface

Build system defines __ANDROID_VENDOR_API__ for non-system modules.
Use this flag to provide vendor API surface for vendor or product
variant modules.

Bug: 368559337
Test: atest AImageReaderWindowTest
Change-Id: I7da3d4ca9f92255a426af8d66b4391f3c1426759
1 file changed