Fix overloading for call() method

[sentilesdal]

In web3.py function construction and execution are separated:

doSomething = deployed_contract.functions.doSomething(x)

result = doSomething.call()

This leads to problems if we want to provide typed return values from call() when doSomething() is overloaded:

doSomething_x = deployed_contract.functions.doSomething(x)
doSomething_xy = deployed_contract.functions.doSomething(x,y)


result_x: int = doSomething_x.call()
result_xy: (int, int) = doSomething_xy.call()

For example, if x and xy versions have the same return signature, then we don't want to declare multiple call() methods. If they do, then we want multple methods, but how do we know which one to call? We can't. We either have to provide multiple return signatures or have doSomething(x) and doSomething(x,y) return different call() methods.

A future improvement would be to change the invocation pattern to:

call_options = CallOptions(block_number=1234)
result = deployed_contract.functions.doSomething(...args, call_options=call_options)

For now, if there are multiple return signatures we simply set the return signature to Any and avoid overloading call() all together. This is probably a very edge case and can be improved in the future.