These asserts were put in place to warn us if they got test coverage.
They do since https://swiftshader-review.googlesource.com/38929. All
seven are hit by the new test.

Bug: b/145836207
Change-Id: I1aba531a1d005b48185d0b3ba72b923d2997a88e
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39088
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: David Turner <digit@google.com>