Vault: Make fee logic easier to follow & bug fixes

[buffalu]

• Bug: reward_fee_bps wasn't checked on initialization. Add test to ensure that's within bounds.
• Add tests checking any fees above 10k or larger than config.deposit_withdrawal_fee_cap_bps on init fail
• Rename config fee_cap_bps to deposit_withdrawal_fee_cap_bps
• Moves some fee math to the vault

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 98.42932% with 6 lines in your changes missing coverage. Please review.

Project coverage is 78.76%. Comparing base (f65f042) to head (2599abc). Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
vault_core/src/vault.rs	98.61%	5 Missing :warning:
vault_core/src/config.rs	75.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #89 +/- ## ========================================== + Coverage 78.67% 78.76% +0.09% ========================================== Files 85 85 Lines 8371 8398 +27 ========================================== + Hits 6586 6615 +29 + Misses 1785 1783 -2 ```

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