d/jak2: get script decompiling, no ref tests yet (#1877)

Has boxed array accessing that prevents me from adding anything to ref
tests (the entire file is lambdas so the access pattern that i would
like to ignore happens at the top-level, can't ignore it.

This code actually already has quite a bit of original docstrings so
it's not too bad in that regard considering a `script-context` can have
16 arbitrary objects. It seems they rarely put more than a single object
in the context and the types are usually obvious / are actually type
checked!

test/decompiler/reference/jak2/engine/debug/editable-player_REF.gc

@@ -2005,7 +2005,7 @@
              (when s4-0
                (let ((gp-1 (-> arg3 param 0)))
                  (set! (-> *syntax-context* got-error?) #f)
-                 (eval! *syntax-context* (the-as structure gp-1))
+                 (eval! *syntax-context* gp-1)
                  (when (not (-> *syntax-context* got-error?))
                    (set! (-> s4-0 changed) #t)
                    (cond

test/decompiler/reference/jak2/engine/debug/menu_REF.gc

@@ -684,7 +684,24 @@
   )
 
 ;; definition for function debug-menu-func-decode
-;; ERROR: function was not converted to expressions. Cannot decompile.
+;; WARN: Return type mismatch object vs function.
+;; WARN: Using new Jak 2 rtype-of
+(defun debug-menu-func-decode ((arg0 object))
+  (let ((v1-2 (rtype-of arg0)))
+    (the-as function (cond
+                       ((or (= v1-2 symbol) (= v1-2 type))
+                        (-> (the-as symbol arg0) value)
+                        )
+                       ((= v1-2 function)
+                        arg0
+                        )
+                       (else
+                         nothing
+                         )
+                       )
+            )
+    )
+  )
 
 ;; definition for function debug-menu-make-from-template
 ;; INFO: Used lq/sq