Better optimize storage for StakingRewardPool

[shannonwells]

Problem

Improve storage size and number of read/writes for all operations accessing StakingRewardPool.

Acceptance Criteria

• [x] Rename StakingRewardPool to BoostingRewardPool to better reflect when it is updated (only on ProviderBoost type stake/unstake)
• [ ] Implement suggestion from @wilwade in PR #1972 check unclaimed rewards
• [ ] Take RewardPoolInfo down to just the one field as discussed in same PR.
• [ ] Tests for same
• [ ] Rerun benchmarks