Fix our scoped nested package swallowed by lexically scoped parent

In "use Foo; class Foo::Bar { }" Foo::Bar would be created as child of
the lexically imported Foo class and was thus missing from the globals.
Previous fixes only handled the case when Foo was a stub package, not
when it was a full class.
Remove the special case and fix the follow up bug that we now got a
duplicate symbol when trying to lexically override classes in the
RESTRICTED setting. There's no need to upgrade the main package to a
global if we only want to create a lexically scoped child anyway.

src/Perl6/World.nqp

@@ -1346,7 +1346,7 @@ class Perl6::World is HLL::World {
         my $longname := '';
         if +@parts {
             try {
-                $cur_pkg := self.find_symbol([@parts[0]], :upgrade_to_global);
+                $cur_pkg := self.find_symbol([@parts[0]], :upgrade_to_global($create_scope ne 'my'));
                 $cur_lex := 0;
                 $create_scope := 'our';
                 $longname := @parts.shift();
@@ -3787,7 +3787,7 @@ class Perl6::World is HLL::World {
                     my %sym := @BLOCKS[$i].symbol($final_name);
                     if +%sym {
                         my $value := self.force_value(%sym, $final_name, 1);
-                        if $upgrade_to_global && $value.HOW.HOW.name($value.HOW) eq 'Perl6::Metamodel::PackageHOW' {
+                        if $upgrade_to_global {
                             ($*GLOBALish.WHO){$final_name} := $value;
                         }
                         return $value;