Split the VC into crates making it more modular (#6453)

* Starting to modularize the VC

* Revert changes to eth2

* More progress

* More progress

* Compiles

* Merge latest unstable and make it compile

* Fix some lints

* Tests compile

* Merge latest unstable

* Remove unnecessary deps

* Merge latest unstable

* Correct release tests

* Merge latest unstable

* Merge remote-tracking branch 'origin/unstable' into modularize-vc

* Merge branch 'unstable' into modularize-vc

* Revert unnecessary cargo lock changes

* Update validator_client/beacon_node_fallback/Cargo.toml

* Update validator_client/http_metrics/Cargo.toml

* Update validator_client/http_metrics/src/lib.rs

* Update validator_client/initialized_validators/Cargo.toml

* Update validator_client/signing_method/Cargo.toml

* Update validator_client/validator_metrics/Cargo.toml

* Update validator_client/validator_services/Cargo.toml

* Update validator_client/validator_store/Cargo.toml

* Update validator_client/validator_store/src/lib.rs

* Merge remote-tracking branch 'origin/unstable' into modularize-vc

* Fix format string

* Rename doppelganger trait

* Don't drop the tempdir

* Cargo fmt