De-obfuscate stack traces for errors offline

[elliette]

In #8385, we are de-obfuscating stack traces in process. That means that we are reporting the Dart file and location names of the stack when DevTools encounters an error. However, if you were to try to open a link to any of those locations, it would fail. This is because although we are bundling the source map with the release, we are not including the actual Dart sources.

Another option (as described by @sigmundch) is to still show the obfuscated stack traces in any reported error, but add automation to de-obfuscate them within our tools, e.g. I believe the Dart VM is using a Github action that can be called to de-obfuscate a stack trace reported in a bug.

Note: I'm opening this up to keep track of what is needed if we decide that the changes in #8385 aren't sufficient for our use case.