[Runtime] Re-configure parachain-staking pallet

[sea212]

The values were already discussed in #595 , we decided to postpone applying them though because the implications are not known yet (which migrations are required, etc.). This is the extracted config (apply on mainnet):

// Staking
/// Rounds before the candidate bond increase/decrease can be executed
pub const CandidateBondLessDelay: u32 = 24;
/// Default fixed percent a collator takes off the top of due rewards
pub const DefaultCollatorCommission: Perbill = Perbill::from_percent(20);
/// Blocks per round
pub const DefaultBlocksPerRound: u32 = 2 * BLOCKS_PER_HOUR as u32;
/// Default percent of inflation set aside for parachain bond every round
pub const DefaultParachainBondReservePercent: Percent = Percent::from_percent(30);
/// Rounds before the delegator bond increase/decrease can be executed
pub const DelegationBondLessDelay: u32 = 24;
/// Rounds before the collator leaving the candidates request can be executed
pub const LeaveCandidatesDelay: u32 = 24;
/// Rounds before the delegator exit can be executed
pub const LeaveDelegatorsDelay: u32 = 24;
/// Maximum bottom delegations per candidate
pub const MaxBottomDelegationsPerCandidate: u32 = 50;
/// Maximum delegations per delegator
pub const MaxDelegationsPerDelegator: u32 = 100;
/// Maximum top delegations per candidate
pub const MaxTopDelegationsPerCandidate: u32 = 300;
/// Minimum round length is 20 minutes
pub const MinBlocksPerRound: u32 = BLOCKS_PER_HOUR as u32;
/// Minimum stake required to become a collator
pub const MinCollatorStk: u128 = 1000 * BASE;
/// Minimum stake required to be reserved to be a delegator
pub const MinDelegatorStk: u128 = 100 * BASE;
/// Minimum collators selected per round, default at genesis and minimum forever after
pub const MinSelectedCandidates: u32 = 8;
/// Rounds before the delegator revocation can be executed
pub const RevokeDelegationDelay: u32 = 24;
/// Rounds before the reward is paid
pub const RewardPaymentDelay: u32 = 2;