ExaBGP 'Never trust 0.0 code' release

ExaBGP 5.0.1

This is a bug fix release addressing issues introduced in 5.0.0.

🚨 Critical Fixes

Container ImportError Fix

• Fix: Container startup failure in 5.0.0 - The 5.0.0 Docker container (ghcr.io/exa-networks/exabgp:5.0.0) failed to start with ImportError: cannot import name 'get_root' from
  'exabgp.version'
• Added missing get_root() and get_zipapp() functions that were removed during 5.0.0 release but still required by application/version.py
• All exabgp commands (--help, version, etc.) now work correctly

RIB Stability Fixes

• Fix: RIB iterator crash in delete_cached_family() - Modified dictionary during iteration causing RuntimeError on configuration reload
• Fix: RIB iterator safety in cached_changes() - Prevented iterator corruption during concurrent access
• Fix: race condition in RIB updates() generator - Fixed missing/duplicate route updates when API flush commands arrive during peer sending

✨ Testing Improvements

• Added comprehensive RIB stress test suite (tests/unit/test_rib_stress.py) - 18 tests covering critical bugs, race conditions, edge cases, and performance