Implement a wrapper for GDB

[sakhnik]

A tiny python proxy would open PTY to allow issuing server commands to GDB or LLDB outside stdin, and return result programmatically without stdout. Conveniently, GDB allows to bypass command history by prefixing commands with server.
Consider naming custom commands in a specific manner <start,end> for easier concealment.

• How to bypass history in LLDB?
• Is it possible to pass commands to LLDB without touching stdin/stdout?
• Pass all the input to the underlying CLI app
• Parse command output and cut off everything between x-nvim-gdb- and next GDB/LLDB prompt
• Move debugger initialization commands to the wrapper

[sakhnik]

LLDB needs an ticket on its own