[IMP] component: do not set props in root components

Also remove props from Fiber, as it was not useful anymore.

tests/component/__snapshots__/component.test.ts.snap

@@ -1036,7 +1036,7 @@ exports[`random stuff/miscellaneous t-on with handler bound to dynamic argument
     var h = this.h;
     let c1 = [], p1 = {key:1};
     var vn1 = h('div', p1, c1);
-    var _2 = context['props'].items;
+    var _2 = context['items'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
     var _3 = _4 = _2;
     if (!(_2 instanceof Array)) {