Do not pass a zero sample count to the backend.
Do not pass a zero sample count to the backend.

FrameGraphTexture::Descriptor uses "0" to mean "auto" but the
sample count that is passed to the backend should always be 1 or
greater.

See also #2957.

google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament