feat: add `extractor` functions with better API than `extract` #968

Job	Run time
get-leptos-changed / Detect Source Change	8s
CI (integrations/actix) / Run ci (nightly)	15m 46s
CI (integrations/axum) / Run ci (nightly)	18m 22s
CI (integrations/utils) / Run ci (nightly)	15m 24s
CI (integrations/viz) / Run ci (nightly)	16m 10s
CI (leptos) / Run ci (nightly)	1h 28m 9s
CI (leptos_config) / Run ci (nightly)	14m 30s
CI (leptos_dom) / Run ci (nightly)	31m 2s
CI (leptos_macro) / Run ci (nightly)	35m 29s
CI (leptos_reactive) / Run ci (nightly)	38m 35s
CI (leptos_server) / Run ci (nightly)	31m 52s
CI (meta) / Run ci (nightly)	15m 27s
CI (router) / Run ci (nightly)	18m 40s
CI (leptos_hot_reload) / Run ci (nightly)	14m 35s
CI (server_fn) / Run ci (nightly)	16m 56s
CI (server_fn_macro) / Run ci (nightly)	16m 52s
CI (server_fn/server_fn_macro_default) / Run ci (nightly)	17m 36s
	6h 45m 33s

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