Integrate WGSL debugger

[greggman]

Tint now has a WGSL debugger. It would be great to integrate it with this debugger.

The first step would just be to integrate as is (lldb style interaction). You'd choose a draw/compute call you want to debug and it would run the trace to that point then hand off all of the relevant data to the WGSL debugger and pop open a REPL.

the second step might be to add the debugger adapter protocol to the tint WGSL debugger library and use that to provide a more devtool like experience with UI to show stack, variables, watches, set breakpoints, etc...