* Use `sp-application-crypto` when generating test justifications

* Try to justifications tests compiling

* Try using `ed25519_dalek` for justification creation

* Small cleanup

* Correctly generate a Keypair

The public key didn't correspond to what would be derived
with the given private key.

* Remove enum index hack

* Clean up test account helper functions

* Fix tests in `pallet-finality-verifier`

* Get `pallet-substrate-bridge` tests compiling again

* Use the correct keyring in justification tests

* Clean up Keyring related code a bit

* Appease Clippy

* Remove unused import

* Use keyring variants directly

* Remove unecessary From implementation

* Move justification module to header-chain primitives crate

* Get justification module compiling in new location

* Get justification module tests compiling

* Use justification code from `header-chain` crate

Mostly compiles, having issues with std/test feature flags across crates.

* Move some code around

* Move justification tests to integration testing crate

* Add `test-utils` crate

* Remove tests and test-helper module from justification code

* Use `test-utils` in Substrate bridge pallet tests

* Remove `sp-keyring` related code from `pallet-substrate-bridge`

* Remove `helpers` module from `pallet-substrate-bridge`

* Add some documentation

* Add more documentation

* Fix typo

Co-authored-by: Tomasz Drwięga <[email protected]>

Co-authored-by: Tomasz Drwięga <[email protected]>