Add simple chat application

[vbmade2000]

This commit adds a simple chat server and a CLI client.

Workspace is divided into 4 crates.

1. server - A chat server.
2. client - A chat client.
3. common - A crate containing common functionalities.
4. integration_tests - A crate containing integration tests.

Both Client and Server use tokio crate for asynchronous development.

(Potential) issues with code.

1. Integration tests are written but not executable as they are unreliable.
2. Although tracing crate is used for logging but it may make increase memory footprint.
3. In logging, tracing span is not removed and it remains with every function call. So for each client, every next log contains current span info plus previous span info. Big issue IMHO. For now, no idea why it is happening and how to solve it.

cargo run -p server -- --ip <IP> --port <PORT>

cargo run -p cli-client -- --host <IP> --port <PORT> --username <username> or
SIMPLE_CHAT_SERVER_HOST=<IP> SIMPLE_CHAT_SERVER_PORT=<PORT> cargo run -p cli-client -- --username <USERNAME>

cargo build --release
cargo test

simple-chat.mp4