Added support for VK_FORMAT_A1R5G5B5_UNORM_PACK16 in the Blitter.

Passes all tests in:
[dEQP-VK.api.copy_and_blit.core.blit_image.all_formats.color]
.b4g4r4a4_unorm_pack16.a1r5g5b5_unorm_pack16.*
.r8g8_snorm.a1r5g5b5_unorm_pack16.*
.a8b8g8r8_unorm_pack32.a1r5g5b5_unorm_pack16.*
.a8b8g8r8_snorm_pack32.a1r5g5b5_unorm_pack16.*

Bug b/119620767

Change-Id: I366cb5697b60b4f0fb51931a6be7b8732cf789ec
Reviewed-on: https://swiftshader-review.googlesource.com/c/23328Reviewed-by: Corentin Wallez <cwallez@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>