`msg-sim` Linux implementation

[thedevbirb]

Spin up a simulated endpoint with proper network emulation settings on Linux

Tasks

• [x] Allow creation of network namespace and devices with delay, loss and bandwidth config
• [x] Allow some code to run in a scope where there is a different namespace
• [x] Manage simulator and simulations to allows tests to run in parallel
• [x] Apply network emulation config also to host environment to be consistent with MacOS behavior
• [x] Docs + how to run tests with sudo on Linux
• [x] Cleanup

Closes #58

[thedevbirb]

@mempirate it hurts me to see this still open. While this is a Linux implementation, we tried to keep feature parity (for what's possible) with the MacOS version, and some stuff broke on the MacOS target.

Given the current usage of this library, I think we need to be a bit more pragmatic and decide to support just one and well, ideally Linux.