Implement .hyper|race.invert properly

- in HyperSeq/RaceSeq
- actual handler in HyperRaceSharedImpl
  - which is actually just a front end for .map

Also unify the order of methods in HyperSeq/RaceSeq with each other for
better maintainability.

src/core/HyperSeq.pm6

@@ -23,14 +23,18 @@ my class HyperSeq does Iterable does Sequence {
             self, $!work-stage-head, $matcher, %options
     }
 
-    method hyper(HyperSeq:D:) { self }
+    method invert(HyperSeq:D:) {
+        Rakudo::Internals::HyperRaceSharedImpl.invert(self, $!work-stage-head)
+    }
 
-    method is-lazy() { False }
+    method hyper(HyperSeq:D:) { self }
 
     method race(HyperSeq:D:) {
         RaceSeq.new(:$!configuration, :$!work-stage-head)
     }
 
+    method is-lazy() { False }
+
     multi method serial(HyperSeq:D:) { self.Seq }
 
     method sink(--> Nil) {

src/core/RaceSeq.pm6

@@ -19,19 +19,24 @@ my class RaceSeq does Iterable does Sequence {
             self, $!work-stage-head, $matcher, %options
     }
 
-    method hyper(RaceSeq:D:) {
-        HyperSeq.new(:$!configuration, :$!work-stage-head)
-    }
-
-    method is-lazy() { False }
-
     method map(RaceSeq:D: $matcher, *%options) {
         Rakudo::Internals::HyperRaceSharedImpl.map:
             self, $!work-stage-head, $matcher, %options
     }
 
+    method invert(RaceSeq:D:) {
+        Rakudo::Internals::HyperRaceSharedImpl.invert:
+            self, $!work-stage-head
+    }
+
+    method hyper(RaceSeq:D:) {
+        HyperSeq.new(:$!configuration, :$!work-stage-head)
+    }
+
     method race(RaceSeq:D:) { self }
 
+    method is-lazy() { False }
+
     multi method serial(RaceSeq:D:) { self.Seq }
 
     method sink(--> Nil) {

src/core/Rakudo/Internals/HyperRaceSharedImpl.pm6

@@ -74,6 +74,11 @@ class Rakudo::Internals::HyperRaceSharedImpl {
                 work-stage-head => Map.new(:$source, :&mapper)
         }
     }
+    multi method invert(\hyper, $source) {
+        hyper.bless:
+          configuration => hyper.configuration,
+          work-stage-head => Map.new(:$source,:mapper(-> Pair:D $p {$p.antipair}))
+    }
 
     my class Sink does Rakudo::Internals::HyperJoiner {
         has Promise $.complete .= new;