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

* change

* recognize vector float product and update tests

test/decompiler/reference/engine/entity/actor-link-h_REF.gc

@@ -267,8 +267,7 @@
               )
              )
             )
-   (let ((v0-1 0))
-    )
+   0
    (none)
    )
   )
@@ -290,8 +289,7 @@
               )
              )
             )
-   (let ((v0-1 0))
-    )
+   0
    (none)
    )
   )

test/decompiler/reference/engine/entity/entity-h_REF.gc

@@ -310,5 +310,4 @@
   )
 
 ;; failed to figure out what this is:
-(let ((v0-20 0))
-  )
+0