Chez Phase 2 (inc U): list? + map-entry-as-vector + clojure.walk (jolt-75sv)

list? was nil on Chez because one cseq record backs both lists and lazy/
realized seqs. Add a list? marker field (cseq v2) set only on the HEAD cell
of a list -- (list ...), quoted list literals, cons, reverse, conj onto a
list. rest/next/seq/map therefore yield unmarked seq cells, so they are
seqs and not list?, matching the seed (where rest-of-a-list is a non-list
seq). Empty () is treated as a list.

vector?: drop the map-entry exclusion. Clojure's MapEntry implements
IPersistentVector and the seed agrees -- (vector? (first {:a 1})) is true.
Only dot-forms' coll dispatch read jolt-vector?, where a 2-vector entry is
correct.

clojure.walk + clojure.template join the prelude stdlib tier. The driver
now evals each stdlib ns's requires -- and the ns form's (:require ...)
clause -- so an aliased ref (template's walk/postwalk-replace) resolves at
emit time instead of lowering to an Unknown class host-static. ns forms are
evaled for that side effect but not emitted, so the runtime *ns* doesn't
leak to the last stdlib ns.

Parity 2163 -> 2176, 0 new divergences. New test/chez/_walk.janet 39/39.

host/chez/jolt-chez.janet

@@ -24,7 +24,8 @@
            "host/chez/natives-str.ss" "host/chez/records.ss"
            "host/chez/host-class.ss"
            "host/chez/host-static.ss" "host/chez/dot-forms.ss"
-           "src/jolt/clojure/string.clj"]
+           "src/jolt/clojure/string.clj" "src/jolt/clojure/walk.clj"
+           "src/jolt/clojure/template.clj"]
     (array/push parts (slurp f)))
   (string/slice (string (hash (string/join parts))) 0))