gpu: isolate tessellation analysis and SPIR-V emission

src/graphics/shader/recompiler/frontend/decode/ShaderDecoder.h

@@ -722,6 +722,7 @@ struct Program {
 Family GetInstructionFamily(uint32_t word);
 // The output object must be freshly initialized.
 void DecodeInstruction(std::span<const uint32_t> code, uint32_t word_index, Instruction& inst);
+Program DecodeFrontProgram(std::span<const uint32_t> front);
 void DecodeProgram(std::span<const uint32_t> code, Program& program);
 bool IsConditionalBranch(Opcode opcode);
 bool IsDirectBranch(Opcode opcode);