Support attaching to sandboxed apps on macOS

## Steps to reproduce
1. On OSX, start a sandboxed application which hosts CoreCLR. See https://developer.apple.com/app-sandboxing/ for documentation.
2. Attach debugger to the process

## Expected behavior
Debugger detects when CoreCLR loads and can successfully debug

## Actual behavior
Debugger never detects that CoreCLR loads

## Notes
Supporting this features requires both CoreCLR and vsdbg changes. On the CoreCLR side, the names of various IPC objects need to be changed to support sandboxing. On the vsdbg side, we need to allow users to specify the application's sandbox id somewhere, and we need to flow it to libdbgshim.dylib.