StakingPool unit tests: constructor & initialize

[roxdanila]

constructor

• Should set nxm, cover and tokenController addresses

initialize

• reverts if cover contract is not the caller
• reverts if initial pool fee exceeds max pool fee
• reverts if max pool fee is 100%
• reverts if product target price is too high
• reverts if product weight bigger than 1
• reverts if products total target exceeds max total weight
• correctly initialize pool parameters
• mints the ownership nft to manager
• correctly initializes the list of products
• works if the list of products params is empty