bug: CompoundERC4626 redeem()

[shortdoom]

Using redeem() on CompoundV2 wrapper with current implementation, leveraging LibCompound, fails to return appropriate assets calculation when calling redeem(). Issue doesn't touch withdraw().

Exchanging totalAsset() implementation from LibCompound's viewUnderlyingBalanceOf() too:

function totalAssets() public view virtual override returns (uint256) {
    return cToken.balanceOf(address(this)).mulWadDown(cToken.exchangeRateStored());
}

fixes shares/assets calculation.

Otherwise, inspecting state change during redeem() yields wrong amount of totalAssets() (AUM), example with hh console.log

totalAssets() 3177334480600619999224 --- with LibCompound
totalAssets() 999999999999801353087 --- with hardcoded division by exchangeRateStored()

I may be missing something as I didn't fully inspect where things go south in LibCompound and my implementation of CompoundWrapper is also protocol specific. Can make a PR later if Issue makes sense.