- Introduce (perhaps poorly named) SpirvRoutine type for
routine-emit-time state (reactor objects).
- Add SpirvShader::emitEarly (intended for definitions that are needed
in shader preamble) and SpirvShader::emit (intended for general actual
code generation) passes.
- Wire up new passes to VertexProgram/VertexRoutine

Change-Id: Iac42eae7dc04adfd4163fd74ba407b613551d14e
Bug: b/120799499
Reviewed-on: https://swiftshader-review.googlesource.com/c/24375Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>