Slienced some bogus clippy warnings in abi_tests.

This file is meant to be expanded in the future(by adding options needed for CI runs), and clippy is complaing about some of that scafolding code.

The warning clippy::never_loop is raised because the command only supports one argument(--help) which stops argument parsing, and prints a message. So, the loop can only iterate once: by either printing the help, or an error message(for invalid options). This is correct, and the loop is still needed to handle new parameters we will add in the future.

clippy::while_let_on_iterator, on the other hand, warns us that this while loop could be rewritten as a for loop. This is true now, because we don't have any parameters with additional arguments. If we want to add a parameter like this:
--abi-cafe-config <path>, we will need to get the path by calling next. This is not possible when using a for loop.