DMG Boot initialization unit test

Description

We should be extensively testing the final state of the DMG and CGB machines after the boot, making the tests as deep as possible

The CGB should be tested more superficially because testing it is proving to be a real challenge.

A good table of expected results can be found here - https://gbdev.io/pandocs/Power_Up_Sequence.html#hardware-registers

⚠ There's already some good work done here: ⚠

https://gitlab.stage.hive.pt/joamag/boytacean/-/blob/master/src/test.rs?ref_type=heads#L82