purge_all allows passing in items' ownership or reference

[TD-Sky]

purge_all implementation for #54 .

The reason why accepting owned items even though we can take only references is compatibility. Refer to #65 (comment) .

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This PR is not fully compatible. It would cause the scene whose type is ambiguous fails compiling, see below:

fn purge_empty() {
    // error!
    trash::os_limited::purge_all(vec![]).unwrap();
}

You need to declare the type:

fn purge_empty() {
    trash::os_limited::purge_all::<Vec<trash::TrashItem>>(vec![]).unwrap();
}

But I believe the scenes are extremely rare in practice.

[TD-Sky]

@oberblastmeister

[Byron]

Thanks a lot, also for pointing out possible compatibility issues.

I learned that in Rust there is a bunch of subtle breaking changes, and some code can even break when another implementation of a trait is added as all of the sudden trait resolution in the calling code is ambiguous.

The improvement is well worth the risk, so let's hope that nobody is actually calling this function with an untyped Vec.