feat: spread component attrs

[Upbolt]

Solves #2403

In the following code Bar will not inherit attributes from Foo when it spreads its attributes

fn main() {
    let (count, set_count) = create_signal(0);

    mount_to_body(move || {
        view! {
            <Foo
                attr:hello=move || count.get().to_string()
            />

            <button on:click=move|_| { set_count.update(|count| *count += 1) }>"+ count"</button>
        }
    });
}

#[component]
fn Foo(#[prop(attrs)] attrs: Vec<(&'static str, Attribute)>) -> impl IntoView {
    view! {
        <Bar {..attrs} />
    }
}

#[component]
fn Bar(#[prop(attrs)] attrs: Vec<(&'static str, Attribute)>) -> impl IntoView {
    view! {
        <div {..attrs}>"hello world"</div>
    }
}

This PR allows for this functionality

[bram209]

This is great, personally I found it confusing that HTML components behaved differently from custom components and think this is a great addition DX wise 👍

[benwis]

Thanks for the PR, can't say I've tried to do this before. Definitely going to try it though