Hold a per Client state rather than a static state.

[Totodore]

Currently the global state management is done with a static state. It is convenient because the user can put non clonable data and get a 'static ref from any callback. However this should be completely avoided for the following reasons:

• With multiple clients spawned, they are going to share the same state and this will probably lead to bugs. First example with all the integration tests for the socketioxide lib.
• Currently the implementation uses unsafe code to do this. Moving to a per client clonable state remove this.
• This will lead to a possible axum-like state implementation. Having only one typed state rather than the type erased typemap.

[Totodore]

If someone want to contribute for this issue:

• Move the state typemap to the Client struct and add a clone bound.
• Pass the typemap to each handler.
• Clone the extracted state from the typemap in the extractor.