Re-split OPL4 PCM instruments due to hardware differences

- MultiPCM also has level direct, so it's remained in DivInstrumentMultiPCM. everything else don't support at MultiPCM is moved into DivInstrumentOPL4PCM.
- MultiPCM can't modify ADSR envelope unless reading instrument from ROM, so I decided to remove ADSR envelope macros. these are moved into OPL4 PCM instrument.
- Save/Load of MultiPCM level direct parameter is still disabled until main version update (for disallow crash).
- Also, this PR fixes OPL4 VGM output.

src/gui/settings.cpp

@@ -4107,6 +4107,7 @@ void FurnaceGUI::drawSettings() {
           UI_COLOR_CONFIG(GUI_COLOR_INSTR_GBA_MINMOD,_("GBA MinMod"));
           UI_COLOR_CONFIG(GUI_COLOR_INSTR_BIFURCATOR,_("Bifurcator"));
           UI_COLOR_CONFIG(GUI_COLOR_INSTR_SID2,_("SID2"));
+          UI_COLOR_CONFIG(GUI_COLOR_INSTR_OPL4_PCM,_("OPL4 PCM"));
           UI_COLOR_CONFIG(GUI_COLOR_INSTR_UNKNOWN,_("Other/Unknown"));
           ImGui::TreePop();
         }