Apply memory decorations from GLSL source to the top-level OpVariable.
Previously, these decorations would only be applied to individual
members. While this is correct behavior, it is more convenient for some
front ends to see the decorations (specifically ReadOnly and WriteOnly)
applied to the whole variable rather than individual members.
It is invalid if the same decoration is applied to the same id multiple
times. This adds a check before adding a decoration that the decoration
is not already in the list. If it is, then the duplicate is not added.
Fixes#3627
UniformAndStorageBuffer8BitAccess capability.
When using the 8-bit storage extension it basically always used the
`UniformAndStorageBuffer8BitAccess` capability, even in cases where it
wasn't required. For instance if we are targeting Vulkan 1.1 (SPIR-V 1.3
or higher), and we are only using 8-bit types in an SSBO, we only need
the `StorageBuffer8BitAccess` capability.
I fixed this by enabling storage buffer use in Vulkan 1.1 / SPIR-V 1.3
or higher, and then changing the logic to match.
I also added some tests that will output different capabilities when run
on Vulkan 1.0 and 1.1, thus they are added twice to the test list (one
for each version).
Fixes#1539
