Chez inc7: namespace :as aliases on the Chez-hosted analyzer

(require '[clojure.string :as s]) then s/foo crashed "Unknown class s": the
Chez analyzer resolved a qualified symbol's ns literally, and there was no
alias table (ns.ss jolt-ns-aliases was a stub, require a no-op). Add an alias
table + chez-register-spec! (parses [ns :as a]) in ns.ss; hc-resolve-cell now
resolves a qualified ns through it; compile-eval pre-registers a form's
require/use :as aliases before analysis (analysis precedes the runtime require,
so the runtime require staying a no-op is fine). The batched gate runner clears
the alias table between cases.

Zero-Janet corpus parity 2159 -> 2240, 0 divergences. spine-test 35/35.

host/chez/driver.janet

@@ -416,6 +416,7 @@
     "                           (var-cell-root-set! (car cr) (cdr cr)))) zj-roots)\n"
     "  (zj-prune! ns-registry zj-ns-base)\n"
     "  (zj-prune! type-registry zj-type-base)\n"
+    "  (hashtable-clear! ns-alias-table)\n"
     "  (when zj-ghier (jolt-invoke (var-deref \"clojure.core\" \"reset!\")\n"
     "                   (var-cell-root zj-ghier) (jolt-invoke (var-deref \"clojure.core\" \"make-hierarchy\"))))\n"
     "  (set-chez-ns! \"user\"))\n"