feat: add timeout handling in TCPClient

[GuillaumeLaine]

Changes

Adds a connection timeout mechanism to the TCPClient constructor to prevent indefinite blocking when connecting to unreachable IP addresses.

Without this change, the first unreachable IP fails quickly and the second connect() call hangs indefinitely, preventing fallback to subsequent IPs. For example:

auto physical_1 = mav::TCPClient(1.1.1.1, 1234);
// Connect failed (Connection refused)

auto physical_2 = mav::TCPClient(2.2.2.2, 1234);
// Hangs indefinitely...

// ...Never reaches subsequent addresses
auto physical_3 = mav::TCPClient(3.3.3.3, 1234);

With this change, all configured IPs will be tried.

For more context, see Trying to connect() multiple times in TCP

[GuillaumeLaine]

Just saw a similar solution was implemented previously here: #47

This PR implements a similar solution by making connect() non-blocking. Additionally, this PR checks on completion of any non-blocking connect() calls before timing out. The linked PR may leave "in progress" connections running in the background. If connect() returns EINPROGRESS, we should use select() to check for completion