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/core-macro/Cargo.toml

@@ -19,7 +19,6 @@ proc-macro2 = { version = "1.0" }
 quote = "1.0"
 syn = { version = "1.0", features = ["full", "extra-traits"] }
 dioxus-rsx = {  path = "../rsx" }
-dioxus-rsx-interpreter = { path = "../rsx_interpreter", optional = true }
 
 # testing
 [dev-dependencies]
@@ -28,4 +27,3 @@ trybuild = "1.0"
 
 [features]
 default = []
-hot-reload = ["dioxus-rsx-interpreter"]