Refactored the handling of usage flags in the VulkanTexture constructor

[mdagois]

• Removed the VK_IMAGE_USAGE_TRANSFER_SRC_BIT and VK_IMAGE_USAGE_TRANSFER_DST_BIT flags that were systematically added to all color and depth attachments.
• Modified the behavior of TextureUsage::BLIT_SRC, TextureUsage::BLIT_DST, and TextureUsage::UPLOADABLE, so that they only raise the corresponding VkImage usage flags.
• Note that I shied away from removing VK_IMAGE_USAGE_SAMPLED_BIT from depth texture with more than 1 sample, as I am not familiar enough with the custom shader-based resolve. I believe we could move the flag to where the depth sidecar is created (using TextureUsage::SAMPLEABLE), but I am not sure 100%.

[mdagois]

NOTE: this PR is meant as a preliminary cleanup for the Support for transient attachments.

[pixelflinger]

looks good but would like @poweifeng to review as well