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/style_attributes.rs

@@ -29,10 +29,10 @@
 - [ ] pub aspect_ratio: Number,
 */
 
-use dioxus_core::Attribute;
 use dioxus_native_core::{
     layout_attributes::parse_value,
     node_ref::{AttributeMask, NodeMask, NodeView},
+    real_dom::OwnedAttributeView,
     state::ParentDepState,
 };
 use dioxus_native_core_macro::sorted_str_slice;
@@ -79,9 +79,14 @@ impl ParentDepState for StyleModifier {
         }
 
         // gather up all the styles from the attribute list
-        for Attribute { name, value, .. } in node.attributes() {
-            if let Some(text) = value.as_text() {
-                apply_style_attributes(name, text, &mut new);
+        if let Some(attrs) = node.attributes() {
+            for OwnedAttributeView {
+                attribute, value, ..
+            } in attrs
+            {
+                if let Some(text) = value.as_text() {
+                    apply_style_attributes(&attribute.name, text, &mut new);
+                }
             }
         }