moved callback to leptos root and improved design #873

Job	Run time
get-leptos-changed / Detect Source Change	7s
CI (integrations/utils) / Run ci (nightly)	15m 29s
CI (integrations/axum) / Run ci (nightly)	16m 25s
CI (integrations/actix) / Run ci (nightly)	17m 31s
CI (leptos_config) / Run ci (nightly)	18m 34s
CI (integrations/viz) / Run ci (nightly)	19m 39s
CI (leptos) / Run ci (nightly)	1h 40m 43s
CI (leptos_dom) / Run ci (nightly)	24m 37s
CI (leptos_hot_reload) / Run ci (nightly)	17m 32s
CI (leptos_macro) / Run ci (nightly)	28m 23s
CI (leptos_reactive) / Run ci (nightly)	40m 38s
CI (leptos_server) / Run ci (nightly)	31m 25s
CI (meta) / Run ci (nightly)	16m 19s
CI (router) / Run ci (nightly)	19m 11s
CI (server_fn) / Run ci (nightly)	19m 5s
CI (server_fn_macro) / Run ci (nightly)	16m 50s
CI (server_fn/server_fn_macro_default) / Run ci (nightly)	15m 22s
	6h 57m 50s

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