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/native-core/src/state.rs

@@ -1,10 +1,11 @@
 use std::{cmp::Ordering, fmt::Debug};
 
 use anymap::AnyMap;
-use dioxus_core::ElementId;
+use dioxus_core::GlobalNodeId;
 use fxhash::FxHashSet;
 
 use crate::node_ref::{NodeMask, NodeView};
+use crate::real_dom::NodeData;
 use crate::traversable::Traversable;
 
 /// Join two sorted iterators
@@ -206,12 +207,16 @@ pub trait NodeDepState<DepState = ()> {
 /// Do not implement this trait. It is only meant to be derived and used through [crate::real_dom::RealDom].
 pub trait State: Default + Clone {
     #[doc(hidden)]
-    fn update<'a, T: Traversable<Node = Self, Id = ElementId>>(
-        dirty: &[(ElementId, NodeMask)],
+    fn update<
+        'a,
+        T: Traversable<Node = Self, Id = GlobalNodeId>,
+        T2: Traversable<Node = NodeData, Id = GlobalNodeId>,
+    >(
+        dirty: &[(GlobalNodeId, NodeMask)],
         state_tree: &'a mut T,
-        vdom: &'a dioxus_core::VirtualDom,
+        rdom: &'a T2,
         ctx: &AnyMap,
-    ) -> FxHashSet<ElementId>;
+    ) -> FxHashSet<GlobalNodeId>;
 }
 
 impl ChildDepState for () {