Resolve symlinks when running debugger in bazel sandbox

[koenlek]

I'm using bazel to build and run my python code. Bazel creates a 'runfiles' directory, which is used as a sandbox that contains all the runtime deps of my command. This runfiles directory is mainly made up by files that are symlinked into the directory.

When I run such code under the ptvsd debugger, it will open the file using the symlink path (i.e. the path in the runfiles directory), which is the same file as what I have in my git workspace. Luckily, it picks up my breakpoints as set on the original file properly, but it feels a bit messy, because:

1. I often end up with two open copies per file: the one from my git workspace, and the one from the runfiles directory (which luckily is a symlink)
2. Visually the UI doesn't sync both files well: break points set in either file will work, but will only show in one of both files...

Perhaps we could add a debug option: "dereference_symlinks"? If true, we make VSCode resolve the symlink to it's original path (readlink -f path/to/symlink)?

Note: my main use case is on Linux, but I think it should be straightforward to make this work on MacOS and Linux. For Windows I'm not so sure. I believe bazel has some experimental symlink runfiles support for Windows, so it might depend on that.

[koenlek]

Related feature request: microsoft/vscode#130082

[brettcannon]

Moved to #17002