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/rsx/src/component.rs

@@ -23,7 +23,7 @@ use syn::{
     Token,
 };
 
-#[derive(PartialEq, Eq)]
+#[derive(PartialEq, Eq, Clone, Debug, Hash)]
 pub struct Component {
     pub name: syn::Path,
     pub prop_gen_args: Option<AngleBracketedGenericArguments>,
@@ -174,7 +174,11 @@ impl ToTokens for Component {
         let key_token = match has_key {
             Some(field) => {
                 let inners = &field.content;
-                quote! { Some(format_args_f!(#inners)) }
+                if let ContentField::Formatted(ifmt) = inners {
+                    quote! { Some(#ifmt) }
+                } else {
+                    unreachable!()
+                }
             }
             None => quote! { None },
         };
@@ -193,16 +197,16 @@ impl ToTokens for Component {
 }
 
 // the struct's fields info
-#[derive(PartialEq, Eq)]
+#[derive(PartialEq, Eq, Clone, Debug, Hash)]
 pub struct ComponentField {
     pub name: Ident,
     pub content: ContentField,
 }
 
-#[derive(PartialEq, Eq)]
+#[derive(PartialEq, Eq, Clone, Debug, Hash)]
 pub enum ContentField {
     ManExpr(Expr),
-    Formatted(LitStr),
+    Formatted(IfmtInput),
     OnHandlerRaw(Expr),
 }
 
@@ -211,7 +215,7 @@ impl ToTokens for ContentField {
         match self {
             ContentField::ManExpr(e) => e.to_tokens(tokens),
             ContentField::Formatted(s) => tokens.append_all(quote! {
-                __cx.raw_text(format_args_f!(#s)).0
+                __cx.raw_text(#s).0
             }),
             ContentField::OnHandlerRaw(e) => tokens.append_all(quote! {
                 __cx.event_handler(#e)
@@ -231,7 +235,7 @@ impl Parse for ComponentField {
         }
 
         if name == "key" {
-            let content = ContentField::ManExpr(input.parse()?);
+            let content = ContentField::Formatted(input.parse()?);
             return Ok(Self { name, content });
         }
         if input.peek(LitStr) {