shader: Properly scale image reads and add GL SPIR-V support

Thanks for everything!

src/shader_recompiler/ir_opt/collect_shader_info_pass.cpp

@@ -432,6 +432,7 @@ void VisitUsages(Info& info, IR::Inst& inst) {
         break;
     case IR::Opcode::ResolutionDownFactor:
     case IR::Opcode::IsTextureScaled:
+    case IR::Opcode::IsImageScaled:
         info.uses_rescaling_uniform = true;
         break;
     case IR::Opcode::LaneId:

src/shader_recompiler/ir_opt/rescaling_pass.cpp

@@ -129,8 +129,7 @@ void PatchImageFetch(IR::Block& block, IR::Inst& inst) {
 void PatchImageRead(IR::Block& block, IR::Inst& inst) {
     IR::IREmitter ir{block, IR::Block::InstructionList::s_iterator_to(inst)};
     const auto info{inst.Flags<IR::TextureInstInfo>()};
-    // TODO: Scale conditionally
-    const IR::U1 is_scaled{IR::Value{true}};
+    const IR::U1 is_scaled{ir.IsImageScaled(ir.Imm32(info.descriptor_index))};
     ScaleIntegerCoord(ir, inst, is_scaled);
 }