This change switches the internal enums we pass around from VkFormat
to FormatID. The end goal of the refactor is to allow the Vulkan
back-end to store packed tables indexed by FormatID. Because VkFormat
has large gaps in its enum space we'd otherwise need to use unordered
data structures like unordered_map.

The change removes the redundant VkFormat storage from vk::Format and
uses a new table query to return the VkFormat that 1:1 matches an
angle::FormatID. We also include a reverse mapping for use with native
Vulkan get functions for Android.

Also moves sRGB conversion functions into renderer_utils. A couple
sRGB formats that don't exist in GL are no longer handled by the sRGB
conversion functions. These formats should be extremely rare.

Bug: angleproject:5438
Change-Id: Id8b49773ca0c556f9f5a6a10fcf0d9762b93bbea
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2618204
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Ian Elliott <ianelliott@google.com>