Fix QuantStamp Audit S1: Missing Input Validation

[gnarvaja]

From QS Audit Report:

The following is a list of places that can potentially benefit from stricter input validation:

1. SwapStableInvestStrategy.sol:
   a. the decimal asset_ of the constructor() function should be less than 18 .
   b. the decimal investAsset_ of the constructor() function should be less than 18 .
   c. the swapConfig.maxSlippage of the _setSwapConfig should be less than WAD .

2. AccessManagedMSV.sol:
   a. the asset_ of initialize() should not be zero address.

3. CompoundV3InvestStrategy.sol:
   a. the inputs of constructor() should not be zero addresses.

Validations 1.a and 1.b implemented. Also, I added a validation to check that asset_ != investAsset_.

I decided not to implement the maxSlippage validation, because I don't think is needed and also I don't wan't to break the abstraction of the SwapLibrary with the swap config. In any case, the setSwapConfig must be used wisely, adding a <WAD validation doesn't add much protection.

Regarding point 2, I decided not to apply the validation, since the parameter is sent to OZ's ERC4626 contract and they decided not to add that validation. Also, other validations of the initialization will forbid deploying a vault with asset = address(0).

Regarding point 3, I implemented a validation around the rewardManager parameter. If cToken_ parameter is zero, the constructor will fail anyway.