Consider deprecating CRDPMultiplexor

[pavelfeldman]

Following commits introduced extra parameter for the CDP multiplexing:

core: c72e33f

debug: microsoft/vscode-chrome-debug@9e04d17

If that was done for Chrome, it can be deprecated - Chrome supports multiple CDP clients out of the box.

[roblourens]

This was done for VS, I think before Chrome supported multiple clients, but I'm not sure they even are still using it. @digeff

[digeff]

This is not needed any more (We have a backlog item to remove it)