Always use ABitmap_compressWithGainmap in screencap

AndroidBitmap_compress() calls into ABitmap_compressWithGainmap anyways,
but has additional checks to ban private bitmap formats from the NDK.
But we still want to enable 10-bit BGRA.

Bug: 431746508
Flag: com.android.graphics.surfaceflinger.flags.readback_screenshot
Test: adb screencap --preserve-display-colors
Change-Id: I278eb237da40620234e441f2aaf8c48d580f55b9