Detect all texture sampling shader instructions.

Change-Id: If557db7db89659e6c2b043b21e5712fb34eafd8d
Reviewed-on: https://swiftshader-review.googlesource.com/4561
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>