feat: write a debugging tool for mapping object pool entries back to lines of code

[eseidel]

We had a customer who had 150k object pool entries in their snapshot.

I believe most of them came from: https://raw.githubusercontent.com/shawnlauzon/latLngToTimezone/refs/heads/master/lib/src/lat_lng_to_timezone.dart

Which creates a zillion objects in the pool. (Should create a simple dart example to test and file an upstream bug.)

Finding that that was the package was difficult and would be aided by some code that could map back to line numbers.