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.lock

@@ -1322,7 +1322,6 @@ checksum = "edca88bc138befd0323b20752846e6587272d3b03b0343c8ea28a6f819e6e71f"
 dependencies = [
  "async-trait",
  "axum-core 0.4.5",
- "axum-macros",
  "base64 0.22.1",
  "bytes",
  "futures-util",
@@ -1415,17 +1414,6 @@ dependencies = [
  "tower-service",
 ]
 
-[[package]]
-name = "axum-macros"
-version = "0.4.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "57d123550fa8d071b7255cb0cc04dc302baa6c8c4a79f55701552684d8399bce"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn 2.0.98",
-]
-
 [[package]]
 name = "axum-server"
 version = "0.7.1"
@@ -3870,6 +3858,7 @@ name = "dioxus-examples"
 version = "0.6.3"
 dependencies = [
  "async-std",
+ "axum 0.7.9",
  "base64 0.22.1",
  "ciborium",
  "dioxus",