Implement __hash__ and __eq__ methods in IdentifiedNode

[ticapix]

Summary of changes

Attempt to fix #1332 and #3338

Checklist

• Checked that there aren't other open pull requests for the same change.
• Checked that all tests and type checking passes.
• If the change has a potential impact on users of this project:
  • Added or updated tests that fail without the change.
  • Updated relevant documentation to avoid inaccuracies.
  • Considered adding additional documentation.
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[edmondchuc]

@ticapix would you be able to add some tests to demonstrate the changes address the two issues mentioned?