media/gpu: Fix Protected Vulkan floating point issues on 10-bit

Increase precision of detiling coordinate variables and linear indices.
Mediump is insufficient for 4K resolution on some GPUs and will result
in artifacts.

Bug: b:345814741
Test: Manual testing on Geralt

Change-Id: Ied150d531f3109e862f514a4c0678b96e0b1839d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5617790


Reviewed-by: Jeff Kardatzke <jkardatzke@google.com>
Commit-Queue: Justin Green <greenjustin@google.com>
Cr-Commit-Position: refs/heads/main@{#1313031}