[GEN] Backport BitFlags where applicable

[tomsons26]

ObjectStatusMaskType, UpgradeMaskType, (and others?) are BitFlags in ZH, basic types with bitshifts in Gen.
Changing Gen to use BitFlags would significantly simplify unifying Gen and ZH codebases

[xezon]

tomsons26

A bit more destructive but must be taken step is to change bitfields to bitflags where ZH did that. I'm not gonna take that up tho cause compilation takes forever on my PC so I can't decently test that. For who will I'd recommend doing it in steps, per BitFlags. Instead of all at once. Upgrade BitFlags may be smallest change I guess. ObjectStatusType will be a big one

I wonder if there's a middle ground. Make a BitFieldFlags class that mimicks calls of BitFlags, but underneath is the bit shifting and masking. Then we get a cleaner diff without the need to currently regression check. After that when we do decide to regression check we just change the type to BitFlags. And no other changes are needed. Yeah that may be a good way to approach this really. We get the cleaner diff to ZH benefits with no regression cost