Codegen floe positions in #%deforestable

The function positions in deforestable operations are Racket
expr positions, but we want them to be Qi floe positions instead. This
modifies the code generation step to recursively invoke codegen on
these nested floe positions.

qi-lib/flow/core/compiler/1000-qi0.rkt

@@ -397,19 +397,19 @@ the DSL.
     (syntax-parse stx
       [((~datum #%deforestable) ((~datum filter) proc:clause))
        #'(lambda (v)
-           (filter proc v))]
+           (filter (qi0->racket proc) v))]
       [((~datum #%deforestable) ((~datum filter-map) proc:clause))
        #'(lambda (v)
-           (filter-map proc v))]
+           (filter-map (qi0->racket proc) v))]
       [((~datum #%deforestable) ((~datum map) proc:clause))
        #'(lambda (v)
-           (map proc v))]
+           (map (qi0->racket proc) v))]
       [((~datum #%deforestable) ((~datum foldl) proc:clause init:expr))
        #'(lambda (v)
-           (foldl proc init v))]
+           (foldl (qi0->racket proc) init v))]
       [((~datum #%deforestable) ((~datum foldr) proc:clause init:expr))
        #'(lambda (v)
-           (foldr proc init v))]
+           (foldr (qi0->racket proc) init v))]
       [((~datum #%deforestable) ((~datum range) arg:expr ...))
        #'(lambda ()
            (range arg ...))]