Fix: replace pkg/errors.Cause() with a bounded rootCause

[mrizk]

Description

If the telemetry helper funcs EndSpan/DeferEndSpan/RecordError are given an error that implements Cause() err and returns itself, then pkg/errors.Cause goes into an infinite loop. This PR replaces errors.Cause() with a bounded rootCause() helper.

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 💥 Breaking change
• 📝 Documentation
• ♻️ Refactoring
• 🏃‍➡️ Performance
• ✅ Tests
• 🔐 Security
• 🔧 Build/CI

Related Issues

None

Changes

• replace pkg/errors.Cause() with a bounded rootCause() helper
• add unit tests to verify fix

Checklist

• My code adheres to the coding and style guidelines of the project.
• I have performed a self-review of my own code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.

Notes

Not sure if 100 is excessive. Could in theory be much smaller but I didn't want the change to possibly break anything else.

[mrizk]

FYI @franklinkim
also here's the related gotsrpc fix: foomo/gotsrpc#112