Simplify Crab token system

[aurexav]

Refer to #1273.

• Stop inflation on Crab and Pangolin
• Add OnSessionEnd to Config
• Remove RingCurrency, UnixTime, RewardReminder and PayoutFraction from Config
• Infation parameters need to be configured in runtime now

[boundless-forest]

I have some concerns about the payout of the Treasury reward. I haven't seen any test cases to ensure that there is no calculation overflow or potential panic if the Treasury is unable to pay for the 20_000 * UNIT. Others LGTM

[github-actions]

Check 74a6dfe crab-dev

Check runtime version

RuntimeVersion {
    spec_name: "Crab2",
    impl_name: "DarwiniaOfficialRust",
    authoring_version: 0,
-   spec_version: 6404,
+   spec_version: 6402,
    impl_version: 0,
    transaction_version: 0,
    state_version: 0,
}

Check runtime storage

Pallet DarwiniaStaking
+ Entry: StorageEntryMetadata { name: "Exposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 319, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Current stakers' exposure."] }
- Entry: StorageEntryMetadata { name: "Exposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 319, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Current stakers' exposure."] }
+ Entry: StorageEntryMetadata { name: "NextExposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 319, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Next stakers' exposure."] }
- Entry: StorageEntryMetadata { name: "NextExposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 319, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Next stakers' exposure."] }

[github-actions]

Check 74a6dfe darwinia-dev

Check runtime version

RuntimeVersion {
    spec_name: "Darwinia2",
    impl_name: "DarwiniaOfficialRust",
    authoring_version: 0,
-   spec_version: 6404,
+   spec_version: 6402,
    impl_version: 0,
    transaction_version: 0,
    state_version: 0,
}

Check runtime storage

Pallet DarwiniaStaking
+ Entry: StorageEntryMetadata { name: "Exposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 319, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Current stakers' exposure."] }
- Entry: StorageEntryMetadata { name: "Exposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 319, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Current stakers' exposure."] }
+ Entry: StorageEntryMetadata { name: "NextExposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 319, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Next stakers' exposure."] }
- Entry: StorageEntryMetadata { name: "NextExposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 319, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Next stakers' exposure."] }

[github-actions]

Check 74a6dfe pangoro-dev

Check runtime version

RuntimeVersion {
    spec_name: "Pangoro2",
    impl_name: "DarwiniaOfficialRust",
    authoring_version: 0,
-   spec_version: 6405,
+   spec_version: 6406,
    impl_version: 0,
    transaction_version: 0,
    state_version: 0,
}

Check runtime storage

Pallet DarwiniaStaking
+ Entry: StorageEntryMetadata { name: "Exposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 314, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Current stakers' exposure."] }
- Entry: StorageEntryMetadata { name: "Exposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 314, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Current stakers' exposure."] }
+ Entry: StorageEntryMetadata { name: "NextExposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 314, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Next stakers' exposure."] }
- Entry: StorageEntryMetadata { name: "NextExposures", modifier: Optional, ty: Map { hashers: [Twox64Concat], key: UntrackedSymbol { id: 0, marker: PhantomData<fn() -> core::any::TypeId> }, value: UntrackedSymbol { id: 314, marker: PhantomData<fn() -> core::any::TypeId> } }, default: [0], docs: [" Next stakers' exposure."] }

[github-actions]

Check 74a6dfe pangolin-dev

Check runtime version

Check runtime storage

[hackfisher]

LGTM