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

* change

* recognize vector float product and update tests

test/decompiler/reference/engine/debug/assert-h_REF.gc

@@ -62,5 +62,4 @@
 (define *__private-assert-info* (new 'static '__assert-info-private-struct))
 
 ;; failed to figure out what this is:
-(let ((v0-4 0))
-  )
+0

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

@@ -66,5 +66,4 @@
   )
 
 ;; failed to figure out what this is:
-(let ((v0-6 0))
-  )
+0

test/decompiler/reference/engine/debug/debug-sphere_REF.gc

@@ -83,8 +83,7 @@
      )
     )
    )
-  (let ((v0-10 0))
-   )
+  0
   (none)
   )
 
@@ -131,8 +130,7 @@
      (add-debug-line #t arg0 s4-0 s2-0 arg3 #f (the-as rgba -1))
      )
     )
-   (let ((v0-2 0))
-    )
+   0
    (none)
    )
   )

test/decompiler/reference/engine/debug/stats-h_REF.gc

@@ -129,8 +129,7 @@
    (set! (-> obj to-spr-waits) (+ (-> obj to-spr-waits) arg1))
    (set! (-> obj from-spr-waits) (+ (-> obj from-spr-waits) arg2))
    )
-  (let ((v0-0 0))
-   )
+  0
   (none)
   )