Make %h ~~ /foo/ 2x faster, fix @A ~~ /foo/

- make fast internal method using an iterator
- make %h case use that with %h.keys.iterator
- make @A case use that with @a.iterator

This also fixes

  "a"...* ~~ / z /

which was broken with e4dc8b6

src/core/Regex.pm

@@ -34,41 +34,41 @@ my class Regex { # declared in BOOTSTRAP
     }
 
     multi method ACCEPTS(Regex:D \SELF: @a) {
-        nqp::decont(
-          nqp::getlexrelcaller(nqp::ctxcallerskipthunks(nqp::ctx()),'$/') =
+        SELF!ACCEPT-ITERATOR(
+          nqp::getlexrelcaller(nqp::ctxcallerskipthunks(nqp::ctx()),'$/'),
+          @a.iterator
+        )
+    }
+
+    multi method ACCEPTS(Regex:D \SELF: %h) {
+        SELF!ACCEPT-ITERATOR(
+          nqp::getlexrelcaller(nqp::ctxcallerskipthunks(nqp::ctx()),'$/'),
+          %h.keys.iterator
+        )
+    }
+
+    method !ACCEPT-ITERATOR(Regex:D \SELF: \slash, Iterator:D \iter) {
+        nqp::decont(slash =
           nqp::stmts(
-            (my int $elems = @a.elems),  # reifies
-            (my int $i     = -1),
-            nqp::while(
-              nqp::islt_i(($i = nqp::add_i($i,1)),$elems)  # left to check?
-                && nqp::islt_i(                            # invalid match?
+            nqp::until(
+              nqp::eqaddr(                                 # nothing to check?
+                (my $pulled := iter.pull-one),IterationEnd)
+                || nqp::isge_i(                            # valid match?
                      nqp::getattr_i(
-                       (my \cursor := SELF.($cursor-init(Cursor,
-                         nqp::atpos(nqp::getattr(@a,List,'$!reified'),$i),
-                       :c(0)))),Cursor,'$!pos'),
+                       (my \cursor := SELF.($cursor-init(Cursor,$pulled,:0c))),
+                       Cursor,'$!pos'),
                    0),
               nqp::null
             ),
             nqp::if(
-              nqp::iseq_i($i,$elems),
-              Nil,               # exhausted list
+              nqp::eqaddr($pulled,IterationEnd),
+              Nil,               # no match found
               cursor.MATCH       # found it!
             )
           )
         )
     }
 
-    multi method ACCEPTS(Regex:D \SELF: %h) {
-        my $dollar_slash := nqp::getlexrelcaller(
-            nqp::ctxcallerskipthunks(nqp::ctx()),
-            '$/');
-        for %h.keys {
-            $dollar_slash = SELF.(Cursor.'!cursor_init'($_, :c(0))).MATCH_SAVE;
-            return $dollar_slash if $dollar_slash;
-        }
-        Nil;
-    }
-
     multi method Bool(Regex:D:) {
         nqp::stmts(
           (my $ctx := nqp::ctx),