Update reward pool on provider_boost or unstake #1699 (#1948)

The goal of this PR is to update the StakingRewardPool on a `provider_boost` or `unstake` extrinsic call.

Closes #1699

Also includes a bunch of lint changes

- [x] Design doc(s) updated
- [x] Tests added
- [x] Benchmarks corrected and updated
- [x] Weights updated

pallets/capacity/src/tests/unstaking_tests.rs

@@ -232,7 +232,6 @@ fn unstaking_everything_reaps_staking_account() {
 		register_provider(target, String::from("WithdrawUnst"));
 		assert_ok!(Capacity::stake(RuntimeOrigin::signed(staker), target, amount));
 
-
 		run_to_block(1);
 		// unstake everything
 		assert_ok!(Capacity::unstake(RuntimeOrigin::signed(staker), target, 20));