cpu_test.rs - Possibly compress repeating tests.

[Spalynx]

The codebase has many tests that provide the same functionality as another test, but it works on a different opcode/register. This is because many of the low-level opcodes have similar functionalities to another, but operate on different values.
Example:

• STA / STX / STY - All three store their respective values in exactly the same way, and are therefore copy paste jobs. Same goes for testOP_ST-.

The opcodes have use in separate functions, but the tests dont /necissarily/.
Therefore, a possible solution would be to compress the similar tests into one test_OP, but this might affect readability.