Support instantiation_stack when querying

[bmustiata]

In bazel, it is possible to call the cquery with --proto:instantiation_stack.

The instantiation_stack shows where the target is created from and can help a great deal with tracing where things are made. It will return an array with file:column entries from the BUILD.bazel down to the native invoke.

I'd like to have the same for plz query graph to investigate where things get created. I could probably try to implement this myself if some tips are provided on where I should get the stack trace from and how to attach it to the query item.

Thank you for your great product!

[peterebden]

At present we don't have an explicit representation of the call stack available (it's recreated on the fly when errors occur). I can see where it'd be useful, but unsure how it will look to actually implement.