Fix/registers - Githubissues

This PR does the following:

Implements new class - StatResolver, where register_stat_calculators function now lives.
Moves most of the stat calculator resolution from manager to this new class
Moves stats and dependencies of calculators to class-level function meta_info
StatResolver registers all StatCalculators without instantiating
Then inits only stat calculators that are needed for this particular run
NLI model and OpenAIChat are only created once there is need to init calculator that requires it
Stat calculator resolution now triggered only when Manager starts running (call) to make loading saved managers faster
Some refactoring here and there

IINemo / lm-polygraph