RakuAST: Avoid DEPARSE during compilation for better performance

DEPARSE can be surprisingly expensive, so when the compiler needs the
actual source string, just use the origin instead.

src/Raku/ast/code.rakumod

@@ -2007,7 +2007,7 @@ class RakuAST::RegexThunk
         # Create Regex object.
         my $regex := nqp::create(Regex);
         nqp::bindattr($regex, Code, '$!signature', $signature);
-        nqp::bindattr_s($regex, Regex, '$!source', self.DEPARSE);
+        nqp::bindattr_s($regex, Regex, '$!source', self.origin.Str);
         nqp::bindattr($signature, Signature, '$!code', $regex);
         $regex
     }

src/Raku/ast/origins.rakumod

@@ -31,6 +31,10 @@ class RakuAST::Origin {
     method is-key() { nqp::isconcrete($!nestings) ?? True !! False }
 
     method as-match() { $!source.match-from(self) }
+
+    method Str() {
+        nqp::substr($!source.orig, $!from, $!to - $!from)
+    }
 }
 
 # The class is supposed to mimic NQPMatch up to the level to make it usable as QAST::Node.node value.
@@ -192,4 +196,4 @@ class RakuAST::Origin::Source {
             :line(@location[0]), :file(@location[2]),
             :orig-line(self.original-line($from)))
     }
-}
+}

src/Raku/ast/statementprefixes.rakumod

@@ -622,7 +622,7 @@ class RakuAST::StatementPrefix::Phaser::Pre
                       value => RakuAST::StrLiteral.new(
                         $condition
                           ?? nqp::hllizefor($condition, 'Raku')
-                          !! $blorst.DEPARSE
+                          !! $blorst.origin.Str
                       )
                     )
                   )
@@ -691,7 +691,7 @@ class RakuAST::StatementPrefix::Phaser::Post
                             value => RakuAST::StrLiteral.new(
                               $condition
                                 ?? nqp::hllizefor($condition, 'Raku')
-                                !! $blorst.DEPARSE
+                                !! $blorst.origin.Str
                             )
                           )
                         )