Make IdentityInfo generic in pallet-identity (#1661)

Fixes #179 

# Description

This PR makes the structure containing identity information used in
`pallet-identity` generic through the pallet `Config`. Additionally, the
old structure is now available in a separate module called `simple`
(pending rename) and is compatible with the new interface.

Another change in this PR is that while the `additional` field in
`IdentityInfo` stays for backwards compatibility reasons, the associated
costs are stil present in the pallet through the `additional` function
in the `IdentityInformationProvider` interface. This function is marked
as deprecated as it is only a temporary solution to the backwards
compatibility problem we had. In short, we could have removed the
additional fields in the struct and done a migration, but we chose to
wait and do it off-chain through the genesis of the system parachain.
After we move the identity pallet to the parachain, additional fields
will be migrated into the existing fields and the `additional` key-value
store will be removed. Until that happens, this interface will provide
the necessary information to properly account for the associated costs.

Additionally, this PR fixes an unrelated issue; the `IdentityField` enum
used to represent the fields as bitflags couldn't store more than 8
fields, even though it was marked as `#[repr(u64)]`. This was because of
the `derive` implementation of `TypeInfo`, which assumed `u8` semantics.
The custom implementation of this trait in
https://github.com/paritytech/polkadot-sdk/commit/0105cc0396b7a53d0b290f48b1225847f6d17321
fixes the issue.

---------

Signed-off-by: georgepisaltu <george.pisaltu@parity.io>
Co-authored-by: Sam Johnson <sam@durosoft.com>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>

substrate/bin/node/runtime/src/lib.rs

@@ -60,6 +60,7 @@ use node_primitives::{AccountIndex, Balance, BlockNumber, Hash, Moment, Nonce};
 use pallet_asset_conversion::{NativeOrAssetId, NativeOrAssetIdConverter};
 use pallet_broker::{CoreAssignment, CoreIndex, CoretimeInterface, PartsOf57600};
 use pallet_election_provider_multi_phase::{GeometricDepositBase, SolutionAccuracyOf};
+use pallet_identity::simple::IdentityInfo;
 use pallet_im_online::sr25519::AuthorityId as ImOnlineId;
 use pallet_nfts::PalletFeatures;
 use pallet_nis::WithMaximumOf;
@@ -1474,6 +1475,7 @@ impl pallet_identity::Config for Runtime {
 	type SubAccountDeposit = SubAccountDeposit;
 	type MaxSubAccounts = MaxSubAccounts;
 	type MaxAdditionalFields = MaxAdditionalFields;
+	type IdentityInformation = IdentityInfo<MaxAdditionalFields>;
 	type MaxRegistrars = MaxRegistrars;
 	type Slashed = Treasury;
 	type ForceOrigin = EnsureRootOrHalfCouncil;