Fix unittest and code cleanup

[sashacmc]

• fix some notes from Feature/1.5.8/zenoh utransport impl #65
• implement cleanupListener
• change listener storing key
• fix lambda transmission to zenoh

[gregmedd]

Looks good - I don't see anything that is critical to change.

In the future, it might be helpful to split up multiple changes like this. For example, the PR could have contained a commit that just removed the using namespace statements, then another commit that fixed the test failure, and so on. That way a reviewer could look at each change individually if it makes the review easier.

[gregmedd]

Minor: since this code is already inside the uprotocol namespace, the uprotocol:: prefix isn't required. For example, this could be:

Suggested change

	uprotocol::v1::UStatus ZenohUTransport::uError(uprotocol::v1::UCode code,
	std::string_view message) {
	uprotocol::v1::UStatus status;
	v1::UStatus ZenohUTransport::uError(v1::UCode code,
	std::string_view message) {
	v1::UStatus status;