The sample qualifier forces the use of per sample rendering,
so this cl adds a mode for it and detects whether the sample
decoration is used in the shader.

Bug: b/171415086
Change-Id: Ic59eb45c41f019859eff01de4bf467284de53c0a
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/51730Tested-by: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>