core: AwaitTreeLayer covers oio::Read and oio::Write

[Xuanwo]

opendal/core/src/layers/await_tree.rs

Lines 48 to 61 in 248538f

	impl AwaitTreeLayer {
	/// Create a new `AwaitTreeLayer`.
	pub fn new() -> Self {
	Self {}
	}
	}
	impl<A: Access> Layer<A> for AwaitTreeLayer {
	type LayeredAccess = AwaitTreeAccessor<A>;
	fn layer(&self, accessor: A) -> Self::LayeredAccess {
	AwaitTreeAccessor { inner: accessor }
	}
	}

AwaitTreeLayer doesn't support oio::Read and oio::Write now, makes it hard to track read and write process.

[PsiACE]

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