Offchain signing (#5182)

* New approach to offchain signing.

* Use in im-online

* Rewrite to use Account<T>

* DRY signing.

* Implement send_raw_unsigned_transaction

* WiP

* Expunge LocalCall

* Expunge LocalCall

* Fix compilation.

* Solve call.

* Make it compile again.

* Finalize implementation.

* Change CreateTransaction

* Clear CreateTransaction.

* Add price payload

* Send raw transaction

* Submit signed payload / unsigned transaction (WIP)

* Supertrait requirements on T::Signature

* Validate signature of payload on an unsigned transaction

* Fix encoding - part 1

* Make it compile.

* Fix compilation of unsigned validator.

* Pass price payload to the transaction

* Make block number part of the signed payload

* Send signed transaction

* Implement all_accounts, any_account

* Fix formatting

* Implement submit_transaction

* Submit signed transaction (ForAll, ForAny)

* Fix formatting

* Implement CreateSignedTransaction

* Move sign and verify to AppCrypto

* Sign transaction

* Call `use_encoded`

* Remove SubmitAndSignTransaction

* Implement runtime using new SigningTypes

* Adapt offchain example to changes

* Fix im-online pallet

* Quick fix: rename AuthorityId2

* Fix offchain example tests

* Add a comment on why keystore is required in unsigned transaction test

* Use UintAuthorityId instead of u64

* WIP

* Remove IdentifyAccount from UintAuthorityId

* Implement PublicWrapper type

* Fix im-online tests

* Fix runtime test

* Bump spec version

* Fix executor tests

* Rename ImOnlineAuthId -> ImOnlineAuthorityId and formatting

* Fix merge

* Documentation

* Revert u64 -> UintAuthorityId conversion

* Fix string errors

* Document public members in offchain module

* Introduce SubmitTransaction

* Update pallets to use SubmitTransaction

* WIP

* Use SubmitTransaction in offchain

* Use `submit_unsigned_transaction`

* Fix tests

* Update docs

* Remove SigningTypes requirement from `SendTransactionTypes`

* Fix tests

* Update frame/system/src/offchain.rs

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update frame/system/src/offchain.rs

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update frame/example-offchain-worker/src/tests.rs

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update frame/system/src/offchain.rs

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update frame/system/src/offchain.rs

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Remove leftover from previous iterations

* Change enum to struct

* Remove public

* Move mock to node/executor/tests

* Cleanup test-helpers

* Make `application-crypto` `std` feature internal

The macros should not generate code that requires that the calling crate
has a feature with the name `std` defined.

* Revert cargo lock update

* Use TestAuthorityId from common

* Restore members of account to public

* Tidy up imports

* Fix benchmarking pallet

* Add tests demonstrating ForAll, ForAny on signer

* Move definition of AppCrypto

in example-offchain-worker
from tests to mod::crypto

* Cleanup stray comment

* Fix ValidTransaction

* Re-fix CreateSignedTransaction

* Address PR feedback

* Add can_sign method to signer

* Propagate error

* Improve documentation

* Fix vec! macro not available

* Document SendTransactiontypes

* Add some docs.

* Split signing examples

* Add tests for signing examples

* WIP can_sign - PR feedback

* WIP

* Split for_any / for_all into different calls

* Verify payload and signature in test

* Fix can_sign implementation

* Fix impl_version

* Import Box from sp_std

* Create issues for TODOs

* Ignore doctest.

* Add test directly to system. Adjust UintTypes.

* Add some tests to account filtering.

* Remove code samples and point to example offchain worker

* Fix doc links

* Fix im-online tests using signatures.

Co-authored-by: Tomasz Drwięga <tomasz@parity.io>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>