Use the named function arguments syntax for encoding the
nonce in the L1CrossDomainMessenger tests. This reduces
the cognitive overhead of ensuring that the tests
are correct. I had to spend the mental energy figuring out
what the arguments were over and over again so i elimated
the problem by moving to the kargs syntax.

I believe that tests should require the least amount of
mental overhead as possible to confirm their correctness.
This is a single commit that reduces the mental overhead
of ensuring our test suite is correct.