tests: Update processor tests to use mollusk

[febo]

Problem

PR #14 updated the tests crate to use mollusk, but there are few more tests under the processor module.

Solution

Move the processor tests to the tests crate and update them to use mollusk.

[buffalojoec]

I think this approach will definitely work for what we're after.

First of all, it's doing the same thing as the existing tests, with the exception of using real syscall stubs, which is the safest way to port everything over. Furthermore, I believe enabling fixture generation from instruction chains will be quite trivial, so this would still allow us to generate loads of fixtures for conformance testing between different versions of token programs.

The only downside here is that we'll end up generating fixtures for every single "setup instruction" as well as the real instructions we are testing. But that isn't really a problem aside from being redundant.

The obvious alternative here is to use a few helpers that can set up mints, accounts, etc. beforehand and just invoke each Mollusk instance one at a time, but that could introduce a bug along the way in the account setup.

I think this works!