Remove IntKeyOld

[maurolacy]

Remove IntKeyOld

cw-plus/packages/storage-plus/src/keys_old.rs

Lines 9 to 12 in f4b7f25

	pub struct IntKeyOld<T: Endian> {
	pub wrapped: Vec<u8>,
	pub data: PhantomData<T>,
	}

and associated stuff.

And then rename the CwIntKey trait

cw-plus/packages/storage-plus/src/int_key.rs

Lines 7 to 13 in f4b7f25

	// TODO: Rename to `IntKey` after deprecating current `IntKey` (https://github.com/CosmWasm/cw-plus/issues/570)
	pub trait CwIntKey: Sized + Copy {
	type Buf: AsRef<[u8]> + AsMut<[u8]> + Into<Vec<u8>> + Default;
	fn to_cw_bytes(&self) -> Self::Buf;
	fn from_cw_bytes(bytes: Self::Buf) -> Self;
	}

to IntKey for simplicity.