Re-imagine @A[*] to use new infrastructure (60% faster)

This is on top of the 5x that was already achieved by optimizing
the @A[@i] candidates (which the @A[*] was calling internally).
So the whatever slice is now 8x as fast as before.

src/core.c/array_slice.pm6

@@ -357,33 +357,32 @@ multi sub postcircumfix:<[ ]>(\SELF,Callable:D $block,Bool() :$v!,*%other) is ra
 }
 
 # @a[*]
-multi sub postcircumfix:<[ ]>( \SELF, Whatever:D ) is raw {
-    SELF[^SELF.elems];
+multi sub postcircumfix:<[ ]>(\SELF, Whatever:D, *%_) is raw {
+
+    # Get the dispatch index
+    my int $index;
+    if nqp::getattr(%_,Map,'$!storage') {
+        my $lookup := Rakudo::Internals.ADVERBS_TO_DISPATCH_INDEX(%_);
+        if nqp::istype($lookup,X::Adverb) {
+            $lookup.what   = "whatever slice";
+            $lookup.source = try { SELF.VAR.name } // SELF.^name;
+            return Failure.new($lookup);
+        }
+
+        # Good to go!
+        $index = $lookup;
+    }
+
+    # Do the correct processing for given dispatch index
+    Rakudo::Internals.ACCESS-DISPATCH-CLASS($index)
+      .new(SELF).slice(Rakudo::Iterator.IntRange(0,SELF.end))
 }
 multi sub postcircumfix:<[ ]>( \SELF, Whatever:D, Mu \assignee ) is raw {
     SELF[^SELF.elems] = assignee;
 }
 multi sub postcircumfix:<[ ]>(\SELF, Whatever:D, :$BIND!) is raw {
     X::Bind::Slice.new(type => SELF.WHAT).throw;
 }
-multi sub postcircumfix:<[ ]>(\SELF, Whatever:D, Bool() :$delete!, *%other) is raw {
-    SLICE_MORE_LIST( SELF, ^SELF.elems, 'delete', $delete, %other );
-}
-multi sub postcircumfix:<[ ]>(\SELF, Whatever:D, Bool() :$exists!, *%other) is raw {
-    SLICE_MORE_LIST( SELF, ^SELF.elems, 'exists', $exists, %other );
-}
-multi sub postcircumfix:<[ ]>(\SELF, Whatever:D, Bool() :$kv!, *%other) is raw {
-    SLICE_MORE_LIST( SELF, ^SELF.elems, 'kv', $kv, %other );
-}
-multi sub postcircumfix:<[ ]>(\SELF, Whatever:D, Bool() :$p!, *%other) is raw {
-    SLICE_MORE_LIST( SELF, ^SELF.elems, 'p', $p, %other );
-}
-multi sub postcircumfix:<[ ]>(\SELF, Whatever:D, Bool() :$k!, *%other) is raw {
-    SLICE_MORE_LIST( SELF, ^SELF.elems, 'k', $k, %other );
-}
-multi sub postcircumfix:<[ ]>(\SELF, Whatever:D, Bool() :$v!, *%other) is raw {
-    SLICE_MORE_LIST( SELF, ^SELF.elems, 'v', $v, %other )
-}
 
 # @a[**]
 multi sub postcircumfix:<[ ]>(\SELF, HyperWhatever:D $, *%adv) is raw {