Exposing GL_OES_depth_texture requires that at least
depth only format are filterable, so making sure at
least D16_UNORM and D32_SFLOAT can be filtered.

Tests: dEQP-VK.*d16_unorm*
Tests: dEQP-VK.*d32_sfloat*
Bug: b/146563038
Change-Id: I2c5a10b03eab19d179c005e2f0f8f22a4921830c
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39748
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>