[spirv] Add basic infrastructure for negative deserializer tests

We are relying on serializer to construct positive cases to drive
the test for deserializer. This leaves negative cases untested.

This CL adds a basic test fixture for covering the negative
corner cases to enforce a more robust deserializer.

Refactored common SPIR-V building methods out of serializer to
share it with the deserialization test.

PiperOrigin-RevId: 260742733