WIP ARM fees charged on buying base assets

[naddison36]

Changes

• Replace the old performance-fee-on-asset-growth model with swap-only fee accrual, so fees accrue only on discounted base-asset buy swaps.
• Update swap fee math to charge (convertedBaseAmountIn - liquidityAmountOut) * fee / FEE_SCALE on qualifying swaps, including appreciating-base-asset paths like sUSDe -> USDe.
• Change totalAssets() to subtract only stored accrued swap fees instead of fees derived from passive asset growth.
• Replace legacy lastAvailableAssets fee accounting with explicit stored feesAccrued, and stop maintaining the deprecated legacy field after upgrade.
• Reuse the old fee storage slot via a packed FeeData struct that holds fee and feesAccrued in a single slot.
• Keep feesAccrued at a 1 wei sentinel after collection to avoid a more expensive 0 -> nonzero storage write on the next fee-bearing swap.
• Add migration initializers to LidoARM, EtherFiARM, EthenaARM, and OriginARM to clear the reused legacy fee storage during upgrade.
• Preserve the external fee() and feesAccrued() interfaces while moving internal fee state to the packed struct layout.

Gas impact

• Before upgrade, the full Lido stETH -> WETH fee-bearing swap transaction used 96,864 gas.
• After upgrade, the full swap transaction used 105,354 gas.
• Net change: +8,490 gas, which is about an 8.8% increase.

[naddison36]

Closing as this is now in #208