Organize validator set

## Types

Eventually, we will have only 3 types for validators.

1. `ctypes::Validator` - It has two fields: `public_key` and `weight`.
2. `ctypes::ValidatorSet` - It is a newtype of `Vec`, but it save it sorted, and provides methods to save to/load from state. Also, its hash will be directly written in block header.
3. `foundry_graphql_engine::Validator` GraphQL resolver for validator.

All other types will be completely removed. (`NextValidatorSet`, `CurrentValidatorSet`, `SimpleValidator`, `WeightOrderedValidators`, ...)

## Naming

Validators -> Validator set
delegation/deposit/ ... -> weight

## Next / Current
Both will be saved, but share same type `ValidatorSet`.

## Coordinator-Module interface
Will be asked to return only `Vec` as the validator set.

## Test
We have to add various e2e tests that involve multiple nodes + varying validator set.

Beginne damit, die Verwendungen der benannten Validator-Typen (`ctypes::Validator`, `ctypes::ValidatorSet`, `foundry_graphql_engine::Validator`) und der Schnittstelle des Coordinator-Moduls nachzuverfolgen. Überprüfe, wie aktuelle und nächste Validator-Sets gespeichert und gehasht werden, und ermittle anschließend die vorhandenen End-to-End-Test-Einstiegspunkte. Erledigt ist die Aufgabe, wenn veraltete Validator-Typen entfernt sind, beide Sets `ValidatorSet` verwenden und Multi-Node-Tests unterschiedliche Validator-Sets abdecken.

Vom Indexierungsmodell aus dem Issue-Text verfasst.