dAppStakingV3 - Tier Thresolds Derivation

[ipapandinas]

This PR will be merged soon. For additional context, a forum post explains the motivation.

This feature introduces a storage migration from v7 to v8 for pallet dappStaking.

Here are the small breaking changes introduced on types:

TierThreshold enum is updated

• DynamicTvlAmount & FixedTvlAmount variants were deleted,
• DynamicPercentage & FixedPercentage were introduced instead.

enum TierThreshold {
    FixedPercentage { required_percentage: Perbill },
    DynamicPercentage {
        percentage: Perbill,
        minimum_required_percentage: Perbill,
    },
}

Note - Example of Perbill to Percent transformation: 35_700_000 = 3.57%

TierConfig storage value: TiersConfiguration type is refactored

• number_of_slots field is removed,
• tier_thresholds field type is refactored from a vector of TierThresholds to a vector of Balances (u128).

This simplifies tier threshold amounts parsing as now item 0 of the vector refers to tier 1's threshold, item 1 to tier 2's threshold, and so on. The total number of slots can still be compute summing all items in slots_per_tier vector.

[bobo-k2]

Resolved in #1376