Standardize epoch configs

[Longarithm]

EpochConfigs has to be stored and created in the similar fashion as RuntimeConfigStore: folder with YAML configs, each corresponding to its own protocol version. Currently it's quite hard to understand what are the values of fields because they are overridden in many places. Somewhere we even just use constants.

Genesis shouldn't be source of truth because we keep adding new fields there.

More specifically - logic in AllEpochConfig is quite chaotic, e.g. AllEpochConfigTestOverrides applies changes on top of all versions of epoch configs. Not sure if min_stake_ratio must be used in all tests, etc.

Example of relevant work #11252