[decompiler] clean up vector detection and add vector float product detection (#638)

* change

* recognize vector float product and update tests

test/decompiler/reference/engine/game/task/game-task-h_REF.gc

@@ -2,5 +2,4 @@
 (in-package goal)
 
 ;; failed to figure out what this is:
-(let ((v0-0 0))
-  )
+0

test/decompiler/reference/engine/game/task/hint-control-h_REF.gc

@@ -74,5 +74,4 @@
   )
 
 ;; failed to figure out what this is:
-(let ((v0-6 0))
-  )
+0

test/decompiler/reference/engine/game/task/task-control-h_REF.gc

@@ -194,5 +194,4 @@
   )
 
 ;; failed to figure out what this is:
-(let ((v0-8 0))
-  )
+0