create custom CompoundTokenAdapters per InterestRateModel

[thetechnocratic]

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[thetechnocratic]

different cTokens use different InterestRateModels

in Legacy, getBorrowRate returns 2 uint256 values
in JumpRateModel, getBorrowRate returns 1 uint256

    /**
      * @notice Calculates the current borrow interest rate per block
      * @param cash The total amount of cash the market has
      * @param borrows The total amount of borrows the market has outstanding
      * @param reserves The total amount of reserves the market has
      * @return error code (0 = no error), The borrow rate per block (as a percentage, and scaled by 1e18)
      */
    function getBorrowRate(uint cash, uint borrows, uint reserves) external view returns (uint,uint);

vs

    /**
      * @notice Calculates the current borrow interest rate per block
      * @param cash The total amount of cash the market has
      * @param borrows The total amount of borrows the market has outstanding
      * @param reserves The total amnount of reserves the market has
      * @return The borrow rate per block (as a percentage, and scaled by 1e18)
      */
    function getBorrowRate(uint cash, uint borrows, uint reserves) external view returns (uint);

therefore, we need separate token adapters depending on which InterestRateModel a cToken uses. we should modify the LibCompound and add another function account for this.
we should also check the codehash of the InterestRateModel to be sure it hasn't changed without us noticing (and revert the call with InvalidState if it has)