Do a whole bunch of cleanup for mapvisited and intermission related things.

* Move the visitation flags, Record Attack/NiGHTS Attack data, and emblem checking to outside of Y_StartIntermission.
* Y_CleanupScreenBuffer never got called for maps which skip the intermission, leading to a small memory leak; this is now fixed by moving it to G_AfterIntermission.
* Y_FollowIntermission was just G_AfterIntermission with modeattacking specific behaviour, but this is desired for all places where G_AfterIntermission is called, so just merge this into G_AfterIntermission.

Notably, these changes are necessary because there are now three maps in the main SP campaign which do not end with traditional intermissions. As a result, this fixes an issue where Black Core's tracks are not available in the Sound Test (due to MV_BEATEN never being applied).

Also, since I was here: Remove "gotperfect" from recorddata_t. This is a duplicate of `mapvisited[gamemap-1] & MV_PERFECT` which uses more memory. I have kept the new spacing in the gamedata for compatibility with RC1 savedatas, but moved it across to the original method everywhere else.