[perl #131387] `is default` value not applied to attributes by default

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# New Ticket Created by  Zoffix Znet 
# Please include the string:  [perl #131387]
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# <URL: https://rt.perl.org/Ticket/Display.html?id=131387 >


$z is `Nil` without my having to assign anything, while `$!z` is Any. To make 
`$!z` Nil I also have to assign Nil to it:

<Zoffix___> m: my $z is default(Nil); dd $z;    class Foo { has $!z is 
default(Nil); method x { dd $!z } }.new.x
<camelia> rakudo-moar 0c5fe5: OUTPUT: «Nil $z = Nil␤Any $!z = Any␤»