1. add resolver/common.py with constraints_t class holding all constraints
with filtered property views (install, excluded, ignored, pinned,
upgrade, requested) and resolver_base_t abstract base class;
2. refactor resolver/general.py: extend resolver_base_t, resolve() takes
constraints_t, add resolve_specs() classmethod convenience for tests;
3. refactor resolver/solv.py: solv_resolver_t extends resolver_base_t,
fix pkg_spec NameError in error messages, remove duplicate parse_reference;
4. add requested flag to package_constraint_t for tracking user-specified
packages vs reference pins;
5. update test_resolver.py and test_solv_backend.py for new interface;
LLM
d0215504d0