State variables that could be set immutable

[code423n4]

Handle

robee

Vulnerability details

In the following files there are state variables that could be set immutable to save gas.
The list of format , :

    basket in RebalanceManagerV2.sol
    uniSwapLikeRouter in SingleNativeTokenExit.sol
    INTERMEDIATE_TOKEN in SingleNativeTokenExit.sol
    uniSwapLikeRouter in SingleNativeTokenExitV2.sol
    INTERMEDIATE_TOKEN in SingleNativeTokenExitV2.sol
    uniSwapLikeRouter in SingleTokenJoin.sol
    INTERMEDIATE_TOKEN in SingleTokenJoin.sol
    uniSwapLikeRouter in SingleTokenJoinV2.sol
    INTERMEDIATE_TOKEN in SingleTokenJoinV2.sol
    predicateProxy in MintableERC20.sol
    underlying in PolygonERC20Wrapper.sol
    childChainManager in PolygonERC20Wrapper.sol