chore(cbus): add `Send` bound to callback for `tarantool::cbus::Message` (close #165)

Summary

• chore(cbus): add Send bound to callback for tarantool::cbus::Message (close #165 (closed))

cc @d.rodionov @gmoshkin @e-ivkov please review it too

Ensure that

• New code is covered by tests
• API is documented
• Changelog is up to date
• Version is bumped in the appropriate Cargo.toml files