`impl Drop` for host resources in the guest

[syntactically]

The types that hold host resource handles in the guest don't currently have an appropriate impl Drop, so they can be leaked if ownership is not passed back to the host by another host or guest call. We should make sure that when a resource handle to a host resource is dropped in the guest, a hostcall is made to drop it in the host.

[danbugs]

Do we have an example where this can happen in witguest? Could this be helpful for a test?

hyperlight/src/tests/rust_guests/witguest/guest.wit

Lines 73 to 80 in 0b10a39

	interface host-resource {
	resource testresource {
	constructor(init1: string, init2: char);
	append-char: func(x: char);
	}
	roundtrip-own: func(x: own<testresource>) -> own<testresource>;
	return-own: func(x: own<testresource>);
	}