implementing single-shot connection mechanism

[phyBrackets]

Implementing #21

The idea behind connectReflective is to allow a slot to receive its ConnectionHandle as a parameter, enabling it to manage its own connection state, such as disconnecting after execution for a single-shot behavior. To safely manage lifetimes and avoid the lambda being deleted while in use, we used smart pointers for now, but i think we still need to go through the design and safety consideration carefully.