Refactored `stdio.rs` and `stdout` capturing

[AndrewF001]

Hi All!

I would appreciate feedback on the enum approach I've taken for implementing different sources to the driver! This new approach dealt with all the issues that came with stdout capture and having a working unit test to show it in action.

Changes:

• Removed gag & serial_test cargo
• Removed tester dependency in p4-analyzer
• stdio.rs renamed to driver.rs and heavily modified the contents
• Driver has an additional field for different input source: Console, Buffer, TCP (LSP struct is hardcode to Console ATM)
• Working unit test for Buffer driver
• Updated CI yml file
• Updated unit tests

Thanks for the review!