Fix Role and DelegatedRole hashing

[Sachith77]

Description

While going through _payload.py, I noticed that Role.__hash__() fails because it tries to hash keyids (a list) and unrecognized_fields (a dict) directly.

This PR:

• Converts keyids to a tuple before hashing.
• Excludes unrecognized_fields since it may contain nested, unhashable JSON.
• Fixes DelegatedRole.__hash__() using self.path instead of self.paths.
• Converts paths and path_hash_prefixes to tuples before hashing.
• Adds regression tests for hashing, equality, and set usage.

The full test suite passes locally with tox.

I noticed similar patterns in a few other metadata classes, but kept this PR focused on Role and DelegatedRole.

[jku]

yeah, it may have been a mistake to add hash() to begin with, I think it only happened because ruff complained about not having it and it seemed easy to do...

In any case these fixes seem reasonable to me, thanks

[Sachith77]

Thanks for the review and the context on why hash() was added.