Certain SPIR-V capabilities are only available in certain SPIR-V versions
or extensions. Also a SPIR-V capability may implicitly declares other
This commit updates gen_spirv_dialect.py to support generating such
information into SPIRVBase.td. It requires us to topologically sort
all capabilities because now a capability can refer to another one.
This commits also registers a few extensions because their symbols are
used by capability availability.
Note that this commit hasn't updated SPIRVConversionTarget to take
into consideration such relationship yet. That will be done in a