[jak2] combined shadow work PR (#2632)

This PR is a combination of
https://github.com/open-goal/jak-project/pull/2507 and some additional
changes to port Shadow VU1 to OpenGL. As far as I can tell, it's
working.

---------

Co-authored-by: Hat Kid <6624576+Hat-Kid@users.noreply.github.com>

game/kernel/jak2/kmachine.cpp

@@ -708,8 +708,12 @@ void InitMachine_PCPort() {
  * PC port functions END
  */
 
-void PutDisplayEnv(u32 /*ptr*/) {
-  ASSERT(false);
+void PutDisplayEnv(u32 alp) {
+  // we can mostly ignore this, except for one value that sets the 'blackout' amount.
+  auto* renderer = Gfx::GetCurrentRenderer();
+  if (renderer) {
+    renderer->set_pmode_alp(alp / 255.f);
+  }
 }
 
 u32 sceGsSyncV(u32 mode) {