fix: fine grained lock in smoltcp

[Koichi98]

Description

This PR is one of a series of PRs that consolidates #252. This PR implements socket-level locking.

A straightforward approach would be to wrap both meta and socket defined here with Mutex. However, this would make it difficult to return pre-lock objects in SocketSet methods like get() and iter() defined in the same file. Therefore, wrapping each member variable in these structures (meta, socket ) with locks and modifying the rest of the code to accommodate this structure.

Related links

PR #252

How was this PR tested?

In applications/tests/test_network, verified:

• Successfully ran scripts/udp.py for udp_test
• Successfully received 'Hello Awkernel!' using nc command for tcp_connect_test
• Successfully received HTTP response after sending data with nc command for tcp_listen_test

Notes for reviewers

• When wrapping UDP, TCP, and other sockets with mutex, we needed to specify the Send trait as a trait bound for the AnySocket trait that these sockets implement. Are there any potential issues or drawbacks to consider with this approach? (smoltcp/src/socket/mod.rs L118)
• I have made efforts to avoid acquiring multiple locks simultaneously to prevent deadlocks, but would like reviewers to double-check.
• In situations where we need a write lock only for certain code paths within an RwLock, the read lock is released first before acquiring the write lock.
  I would appreciate any feedback on these implementation decisions.