adds feature server_fn_axum that compiles for wasm target (#3840)

The current `axum` feature and `server` feature are incompatible with wasm32-unknown-unknown target
due to:
1. depends on axum features not compatible with wasm
2. SSR requires reading the filesystem for index.html

With this patch I add the `server_fn_axum` feature which disables SSR and enables targeting
wasm32-unknown-unknown with server functions enabled.

Note that for this to work, `server_fn` depends on `inventory` and as stated in this docs depending on
the context you might need to expose and call [`__wasm_call_ctors`](https://docs.rs/inventory/latest/inventory/#webassembly-and-constructors)
(I needed that specifically for cloudflare workers)

change axum_server_fn feature for axum_wasm and include SSR tools there

This change additionaly make axum_server_fn feature additive by exposing a different
`DioxusRouterWasmExt` with only the wasm-compatible parts instead of exposing the
`DioxusRouter` trait under the same name.

Docs are updated to reflect this change.

rename axum_wasm to axum_core and update docs

fix typo

re-enable default-features for axum in dioxus-cli

re-enable axum default-features for liveview

re-enable default-features for axum for playwright-tests

Cargo.toml

@@ -191,7 +191,7 @@ tauri-utils = { version = "=2.1.1" }
 tauri-bundler = { version = "=2.2.3" }
 lru = "0.12.2"
 async-trait = "0.1.77"
-axum = "0.7.0"
+axum = { version = "0.7.0", default-features = false }
 axum-server = { version = "0.7.1", default-features = false }
 tower = "0.4.13"
 http = "1.0.0"
@@ -348,6 +348,7 @@ rand = { version = "0.8.4", features = ["small_rng"] }
 form_urlencoded = "1.2.0"
 async-std = "1.12.0"
 web-time = "1.1.0"
+axum = { workspace = true, default-features = true }
 
 [target.'cfg(target_arch = "wasm32")'.dev-dependencies]
 getrandom = { version = "0.2.12", features = ["js"] }