Subtree memorization / reactive templates (#488)

This commit adds subtree memoization to Dioxus.

Subtree memoization is basically a compile-time step that drastically 
reduces the amount of work the diffing engine needs to do at runtime by
extracting non-changing nodes out into a static "template." Templates 
are then understood by the various renderers in the ecosystem as a 
faster way of rendering the same items. 

For example, in the web, templates are simply a set of DOM Nodes created 
once and then cloned later. This is the same pattern frameworks like Lithtml
and SolidJS use to achieve near-perfect performance. 

Subtree memoization adds an additional level of complexity to Dioxus. The RSX
macro needs to be much smarter to identify changing/nonchanging nodes and
generate a mapping between the Template and its runtime counterparts.

This commit represents a working starter point for this work, adding support 
for templates for the web, desktop, liveview, ssr, and native-core renderers.
In the future we will try to shrink code generation, generally improve 
performance, and simplify our implementation.

packages/tui/src/layout.rs

@@ -4,6 +4,7 @@ use std::rc::Rc;
 use dioxus_core::*;
 use dioxus_native_core::layout_attributes::apply_layout_attributes;
 use dioxus_native_core::node_ref::{AttributeMask, NodeMask, NodeView};
+use dioxus_native_core::real_dom::OwnedAttributeView;
 use dioxus_native_core::state::ChildDepState;
 use dioxus_native_core_macro::sorted_str_slice;
 use taffy::prelude::*;
@@ -84,10 +85,17 @@ impl ChildDepState for TaffyLayout {
             }
         } else {
             // gather up all the styles from the attribute list
-            for Attribute { name, value, .. } in node.attributes() {
-                assert!(SORTED_LAYOUT_ATTRS.binary_search(name).is_ok());
-                if let Some(text) = value.as_text() {
-                    apply_layout_attributes(name, text, &mut style);
+            if let Some(attributes) = node.attributes() {
+                for OwnedAttributeView {
+                    attribute, value, ..
+                } in attributes
+                {
+                    assert!(SORTED_LAYOUT_ATTRS
+                        .binary_search(&attribute.name.as_ref())
+                        .is_ok());
+                    if let Some(text) = value.as_text() {
+                        apply_layout_attributes(&&attribute.name, text, &mut style);
+                    }
                 }
             }