[io grant] Fix .perl for IO::Path and subclasses

Fixes RT#131185: https://rt.perl.org/Ticket/Display.html?id=131185

- Coercer doesn't take any named args; use .new() instead
- Always include $!CWD. Fixes failure to roundtrip Win32 paths that
    start with a slash
- Use right type for subclasses. Given them their own .perl, since
    they don't need to include $!SPEC

src/core/IO/Path.pm

@@ -186,9 +186,7 @@ my class IO::Path is Cool does IO {
           !! qq|"$.path".IO|
     }
     multi method perl(IO::Path:D:) {
-        $!is-absolute  # attribute now set
-          ?? "{$.absolute.perl}.IO({:$!SPEC.perl})"
-          !! "{$.path.perl}.IO({:$!SPEC.perl},{:$!CWD.perl})"
+        self.^name ~ ".new({$.path.perl}, {:$!SPEC.perl}, {:$!CWD.perl})"
     }
 
     method sibling(IO::Path:D: Str() \sibling) {
@@ -777,15 +775,27 @@ my class IO::Path is Cool does IO {
 
 my class IO::Path::Cygwin is IO::Path {
     method new(|c) { self.IO::Path::new(|c, :SPEC(IO::Spec::Cygwin) ) }
+    multi method perl(::?CLASS:D:) {
+        self.^name ~ ".new({$.path.perl}, {:$.CWD.perl})"
+    }
 }
 my class IO::Path::QNX is IO::Path {
     method new(|c) { self.IO::Path::new(|c, :SPEC(IO::Spec::QNX) ) }
+    multi method perl(::?CLASS:D:) {
+        self.^name ~ ".new({$.path.perl}, {:$.CWD.perl})"
+    }
 }
 my class IO::Path::Unix is IO::Path {
     method new(|c) { self.IO::Path::new(|c, :SPEC(IO::Spec::Unix) ) }
+    multi method perl(::?CLASS:D:) {
+        self.^name ~ ".new({$.path.perl}, {:$.CWD.perl})"
+    }
 }
 my class IO::Path::Win32 is IO::Path {
     method new(|c) { self.IO::Path::new(|c, :SPEC(IO::Spec::Win32) ) }
+    multi method perl(::?CLASS:D:) {
+        self.^name ~ ".new({$.path.perl}, {:$.CWD.perl})"
+    }
 }
 
 # vim: ft=perl6 expandtab sw=4