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/node.rs

@@ -61,11 +61,11 @@ impl NodeDepState<()> for PreventDefault {
         _sibling: (),
         _ctx: &Self::Ctx,
     ) -> bool {
-        let new = match node
-            .attributes()
-            .find(|a| a.name == "dioxus-prevent-default")
-            .and_then(|a| a.value.as_text())
-        {
+        let new = match node.attributes().and_then(|mut attrs| {
+            attrs
+                .find(|a| a.attribute.name == "dioxus-prevent-default")
+                .and_then(|a| a.value.as_text())
+        }) {
             Some("onfocus") => PreventDefault::Focus,
             Some("onkeypress") => PreventDefault::KeyPress,
             Some("onkeyrelease") => PreventDefault::KeyRelease,