[ty] Consider object members in protocol comparisons (#27532)
## Summary
Consider attributes inherited from `object` when checking assignability
between protocol types.
- Reuse the same fallback policy in structural comparison and
missing-member fast paths while preserving signature compatibility.
- Preserve fast protocol mismatch rejection by caching `object` member
names and each protocol's non-`object` requirement count.
- Keep `__hash__` excluded because subclasses can disable hashing;
`Iterator[int]` therefore remains incompatible with `Hashable`.
Related to astral-sh/ty#4196.
## Test plan
- Added mdtests for protocol requirements satisfied by
`object.__repr__`.
- Covered incompatible inherited method signatures and both custom and
standard-library hashability requirements.
- Verified the existing many-protocol-members mismatch benchmark retains
its fast rejection path.
