spirv: Tell which opcode or value is unhandled when failing

spirv: Tell which opcode or value is unhandled when failing

v2: When available, include the opcode name too. (Karol)

v3: Use more to_string helpers. (Karol)
    Include the wrong bit_size in those failures.
    Include the capability number in spv_check_supported.
    Provide vtn_fail_with_* macros to avoid noise in the call sites.

v4: Provide macros only for opcode and decoration, which have enough
    usages to justify them. (Jason)

Acked-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Karol Herbst <kherbst@redhat.com>