Support public dir (#4783)

* Add optional static_dir support

- add optional application.static_dir field defaulting to none
- copy configured static directory into web output during build/serve
- document config knob and add unit tests
- force full rebuild when static_dir contents change
- sync removes stale outputs and logs copy activity
- track static manifest next to platform dir

Tests: cargo fmt

* default to public dir to match vite

* static_dir -> public_dir

* wip

* deser as none...

* wip... use .manifest.json

* implement dumb form of asset manifest generation

* implement manifest using asset system directly

* cleanup

* dont create extra asset dir for server

---------

Co-authored-by: Evan Almloff <evanalmloff@gmail.com>
Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>

packages/cli/src/build/mod.rs

@@ -11,6 +11,7 @@
 mod assets;
 mod builder;
 mod context;
+mod manifest;
 mod patch;
 mod pre_render;
 mod request;
@@ -19,6 +20,7 @@ mod tools;
 pub(crate) use assets::*;
 pub(crate) use builder::*;
 pub(crate) use context::*;
+pub(crate) use manifest::*;
 pub(crate) use patch::*;
 pub(crate) use pre_render::*;
 pub(crate) use request::*;