multi currency incentive rewards

[ermalkaleci]

Stash

[xlc]

Also need to add the migration for orml-rewards to karura runtime

[xlc]

Need migration for orml-rewards

[wangjj9219]

plan to use HomaValidatorAllowance to implement the multi-currency reward? But reward accumulation for HomaValidatorAllowance is not periodic.

The definition for PoolId is no longer appropriate. PooId implies the reward currency id(native and stable or other allowance) and accumulation method （periodly by fixed amount ，or the multiple of the base amount and fixed rate, or transfer allowance non-periodicly)

Now, orml_rewards supports to record multi-currency rewards amount with single PoolId,
And the pool share of DexIncentives is equal to DexSaving for the same trading pair.
it's better to refactor PoolId to DEX, Loans and others, and need new storage
map Vec<(reward_currency_id, reward_amount_per_period)>
to record periodic fixed amount reward, and define new enum to imply base amount source, add another storage
map PoolId => Vec<(reward_currency_id, fixed_rate, BaseAmountSourceEnum)> to record the fixed rate and the base amount source. Aggregate these configurations when accumulating periodic multi rewards.

@xlc What do you think?
If need to do, more migrations are required, and I am afraid that testing and front-end modification cannot be completed before this Thursday’s runtime upgrade.