…ests

In our tests we now make sure that the randomly generated addresses don't
conflict with the address of the staking contract and associated tokens.
We also make sure that if there are multiple addresses being used inside
the test, that those don't overlap as well.

This bug in the tests were making the fuzz tests fail occasionally, since
there's only a small chance that the randomly generated addresses overlap

For some of the tests we don't fuzz for random addresses, but rather use
static addresses to impersonate a user. However, we never considered the
fact that these addresses could conflict with the `Finthetix` addresses
as well. So in order to make sure this is not the case, we explicitly
check this in the `setup()` function.

The addresses of the `Finthetix` contracts depend on some random seed.
So we can trust that for a given condition of the codebase, the addresses
will be consistent. Hence we are okay with explicitly failing these tests
in case there is a conflict, since in such a condition we can manually
alter these burner addresses (effectively changing the seed)