Enable sRGB conversion when filtering sRGB images

Tests: dEQP-VK.api.copy_and_blit.core.blit_image.all_formats.generate_mipmaps.*

Bug b/119620767

Change-Id: If56a3f74fbf3ee576d9baab44722a13a1ad0d436
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27288Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>