Make descriptions of .list/.hash more precise

- Only *core* Positional/Associative types can be returned:
    Closes rakudo/rakudo#2199 R#2199
- Fix up remaining POD errors
- Reduce prose on .hash and make it more equivalent to that on .list

doc/Type/Any.pod6

@@ -88,15 +88,15 @@ Defined as:
     multi method list(Any:D \SELF: --> List)
 
 
-Applies the infix L«C<,>|/routine/,»
-operator to the invocant
-and returns the resulting L<List>:
+Applies the infix L«C<,>|/routine/,» operator to the invocant and returns
+the resulting L<List>:
 
     say 42.list.^name;           # OUTPUT: «List␤»
     say 42.list.elems;           # OUTPUT: «1␤»
 
-Subclasses of C<Any> may choose to return any L<Positional> type
-from L«C<.list>|/routine/list>». Use L«C<.List>|/routine/List> to
+Subclasses of C<Any> may choose to return any I<core> type that
+does the L<Positional> role
+from L«C<.list>|/routine/list». Use L«C<.List>|/routine/List» to
 coerce specifically to L<List>.
 
 =head2 method push
@@ -377,15 +377,13 @@ Defined as:
     multi method hash(Any:U: --> Hash:D)
     multi method hash(Any:D: --> Hash:D)
 
-Coerces a type object to an empty L<Hash>.
+When called on a type object, returns an empty L<Hash>. On instances,
+equivalent to assigning the the invocant to a C<%->sigilled variable and
+returning that.
 
-More generally, coerces a defined invocant to something that supports the
-L<Associative> role.  This may be a mutable L<Hash>, but may also be
-an immutable L<Map> or anything else that supports the L<Associative>
-role.  Use the C<.Hash> method if you really want to have a mutable L<Hash>,
-or the C<.Map> coercer if you're happy enough with an immutable L<Map>.
-Use the C<.hash> coercer if you really don't care and want the cheapest
-way to get an object that does the L<Associative> role.
+Subclasses of C<Any> may choose to return any I<core> type that does the
+L<Associative> role from L«C<.hash>|/routine/hash». Use L«C<.Hash>|/routine/Hash» to
+coerce specifically to L<Hash>.
 
 =begin code
 my $d; # $d is Any