OpCopyLogical should do bool<->uint8_t conversions

[seanbaxter]

The purpose of OpCopyLogical is to convert between layout OpTypeStructs (eg for Uniform and StorageBuffer storage classes) and non-layout OpTypeStructs (eg for Function and Private storage classes). Since OpTypeBool isn't a layout type, layouts need to store these as uint8_t and OpINotEqual to get a bool back out. This should be a supported operation of OpCopyLogical, because without it, it won't actually perform layout<->non-layout conversions in a general way.

[johnkslang]

But, it is not formalized in SPIR-V what the physical representation of a Boolean is. E.g., Vulkan uses 32-bit int for storage buffers. I think something needs to remain abstracted here. Or, possibly parameterized, to avoid resorting to member-wise copy when boolean conversions are involved.

[seanbaxter]

OpCopyLogical should do bool<->any integral type. Both types involved in the conversion are explicit, so there's no chance of the operator favoring one boolean representation over another.