Metal Sonic fixes!

* Add more context clues to his fight, including an indicator for which laser attack is being used after chargeup.
* Make missiles able to vectorise him.
* Add another laser orb attack - vertical slice - and change the laser orb sequence to accurately reflect that horizontal is the hardest of the ones in 2.1.
* Optimise TC_BLINK, and fix an issue with TC_ALLWHITE that somehow avoided coming up in testing.
* Fix colorized bosses losing their colorization when flashing, by forcing TC_ALLWHITE.