[FIX] compiler: stop event handlers looking up __owl__ in render context

This is another place where we were looking up the component node in the
rendering context instead of on the component, which causes handlers to
have the wrong this when within a t-call-context.

tests/misc/__snapshots__/portal.test.ts.snap

@@ -240,7 +240,7 @@ exports[`Portal Portal composed with t-slot 3`] = `
   let block1 = createBlock(\`<div block-handler-0=\\"custom\\"><span id=\\"childSpan\\">child2</span></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let hdlr1 = [ctx['onCustom'], ctx];
+    let hdlr1 = [ctx['onCustom'], this];
     return block1([hdlr1]);
   }
 }"