[protocol] Use "upgrades.erc1967.getImplementationAddress" to read the implementation address

Use the newly implemented getImplementationAddress function in the Hardhat plugin to read the implementation address. This is to replace the current workaround to use a locally defined storage slot:

hifi/packages/protocol/tasks/deploy/balanceSheet.ts

Lines 33 to 35 in e4bb653

    
           const balanceSheetImplementation: string = hexStripZeros( 
        
             await ethers.provider.getStorageAt(balanceSheetProxy.address, ERC1967_IMPLEMENTATION_STORAGE_SLOT), 
        
           );

Implemented in 075f9c2.

	const balanceSheetImplementation: string = hexStripZeros(
	await ethers.provider.getStorageAt(balanceSheetProxy.address, ERC1967_IMPLEMENTATION_STORAGE_SLOT),
	);