refactor(SwapAndLock): lock yfi via CoveYFI instead of directly w/ YSD

[penandlim]

Describe your changes

Currently SwapAndLock directly locks YFI via YearnStakingDelegate which does not mint new CoveYFI tokens.

This PR modifies SwapAndLock so it locks YFI via CoveYFI, and sends the newly minted CoveYFI tokens to the treasury set in the YearnStakingDelegate.

Checklist before requesting a review

• Title follows conventional commits style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works
• Newly added functions follow Check-effects-interaction
• Gas usage has been minimized (ex. Storage variable access is minimized)

[github-actions]

Slither report

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Summary

[github-actions]

Changes to gas cost

Generated at commit: 1ee62cf736fe8268b080753287e6c5ee415b9ce8, compared to commit: 08dd75f4bf24156f49a520dc6655ed39e80899bb

🧾 Summary (10% most significant diffs)

Contract	Method	Avg (+/-)	%
DYFIRedeemer	receiveFlashLoan	+1,596 ❌	+1.69%

---

Full diff report 👇

Contract	Deployment Cost (+/-)	Method	Min (+/-)	%	Avg (+/-)	%	Median (+/-)	%	Max (+/-)	%	# Calls (+/-)
SwapAndLock	1,183,769 (+10,534)	dYfiRedeemer setDYfiRedeemer	343 (-22) 23,966 (-6)	-6.03% -0.03%	343 (-22) 63,712 (-12)	-6.03% -0.02%	343 (-22) 76,054 (-6)	-6.03% -0.01%	343 (-22) 76,289 (-6)	-6.03% -0.01%	768 (0) 1,296 (0)
DYFIRedeemer	2,139,607 (0)	massRedeem receiveFlashLoan setSlippage	30,408 (0) 23,419 (0) 24,054 (+36)	0.00% 0.00% +0.15%	441,297 (+15) 96,168 (+1,596) 38,867 (+2)	+0.00% +1.69% +0.01%	440,099 (0) 25,238 (-256) 30,088 (0)	0.00% -1.00% 0.00%	689,094 (0) 279,843 (0) 53,508 (0)	0.00% 0.00% 0.00%	1,545 (0) 1,280 (0) 513 (0)
YearnStakingDelegate	3,639,792 (0)	deposit execute harvest setDepositLimit setGaugeRewardSplit setSwapAndLock treasury withdraw(address,uint256) withdraw(address,uint256,address)	26,589 (0) 27,929 (0) 24,054 (0) 48,062 (0) 25,584 (0) 24,116 (0) 443 (0) 22,081 (0) 22,507 (0)	0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%	127,735 (+1) 137,755 (+147) 311,379 (-16) 48,133 (+1) 35,732 (-1) 47,417 (+2) 446 (+3) 95,290 (+2) 104,740 (-2)	+0.00% +0.11% -0.01% +0.00% -0.00% +0.00% +0.68% +0.00% -0.00%	110,791 (0) 149,225 (0) 352,133 (0) 48,062 (0) 25,856 (0) 47,540 (0) 443 (0) 59,896 (0) 90,250 (0)	0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%	249,863 (0) 149,609 (0) 431,958 (0) 48,434 (0) 54,789 (0) 53,849 (0) 2,443 (+2,000) 172,423 (0) 192,751 (0)	0.00% 0.00% 0.00% 0.00% 0.00% 0.00% +451.47% 0.00% 0.00%	3,334 (0) 268 (0) 1,803 (0) 526 (0) 1,283 (0) 280 (0) 513 (+1) 769 (0) 512 (0)
YearnGaugeStrategy	1,817,865 (0)	deposit redeem report setDYfiRedeemer withdraw	30,717 (0) 293,599 (0) 58,515 (0) 27,506 (0) 74,620 (0)	0.00% 0.00% 0.00% 0.00% 0.00%	291,876 (+18) 300,265 (-1) 302,958 (+1) 75,256 (-4) 176,029 (+123)	+0.01% -0.00% +0.00% -0.01% +0.07%	308,482 (0) 298,435 (0) 69,644 (0) 79,805 (0) 201,040 (0)	0.00% 0.00% 0.00% 0.00% 0.00%	447,268 (0) 308,756 (0) 914,852 (-10) 79,824 (0) 256,348 (0)	0.00% 0.00% -0.00% 0.00% 0.00%	7,938 (0) 769 (0) 5,890 (0) 3,587 (0) 1,792 (0)
GaugeRewardReceiver	1,428,645 (0)	harvest	5,864 (0)	0.00%	293,144 (+157)	+0.05%	350,867 (0)	0.00%	455,946 (0)	0.00%	2,058 (0)
StakingDelegateRewards	1,990,696 (0)	notifyRewardAmount setRewardReceiver	24,268 (0) 45,291 (0)	0.00% 0.00%	104,145 (+3) 45,447 (-1)	+0.00% -0.00%	141,488 (0) 45,519 (0)	0.00% 0.00%	161,736 (0) 45,519 (0)	0.00% 0.00%	527 (0) 257 (0)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.72%. Comparing base (8b90a4e) to head (4a59ad9).
Report is 1 commits behind head on master.

❗ Current head 4a59ad9 differs from pull request most recent head 62314f2. Consider uploading reports for the commit 62314f2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #297      +/-   ##
==========================================
- Coverage   97.75%   97.72%   -0.03%     
==========================================
  Files          19       19              
  Lines         980      969      -11     
  Branches      200      198       -2     
==========================================
- Hits          958      947      -11     
  Partials       22       22              

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