The _PACK32 formats have non-packed equivalents with the exact same data
layout, so there's no reason not to have them support the same features.

Also add missing switch cases to avoid debug asserts, and remove 3-byte
formats which we don't support at all.

Bug: b/158259842
Tests: dEQP-VK.*pack32*
Change-Id: Ie655571d50f1af3d97204466f9053b81e32f1490
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/45908
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>