moved callback to leptos root and improved design #892

Job	Run time
get-leptos-changed / Detect Source Change	8s
CI (integrations/actix) / Run ci (nightly)	17m 44s
CI (integrations/utils) / Run ci (nightly)	16m 28s
CI (integrations/axum) / Run ci (nightly)	15m 55s
CI (leptos) / Run ci (nightly)	1h 14m 8s
CI (integrations/viz) / Run ci (nightly)	16m 34s
CI (leptos_config) / Run ci (nightly)	14m 45s
CI (leptos_dom) / Run ci (nightly)	26m 38s
CI (leptos_hot_reload) / Run ci (nightly)	14m 21s
CI (leptos_macro) / Run ci (nightly)	28m 16s
CI (leptos_reactive) / Run ci (nightly)	42m 42s
CI (leptos_server) / Run ci (nightly)	24m 1s
CI (meta) / Run ci (nightly)	17m 0s
CI (router) / Run ci (nightly)	22m 26s
CI (server_fn) / Run ci (nightly)	15m 55s
CI (server_fn_macro) / Run ci (nightly)	17m 15s
CI (server_fn/server_fn_macro_default) / Run ci (nightly)	14m 34s
	6h 18m 50s

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