Handle CWD as a globally available field

[BenBE]

No description provided.

[BenBE]

The code for *BSDProcessList_updateCwd is identical on DragonFlyBSD, FreeBSD and also NetBSD (AFAIRTFM, plz check @fraggerfox). On OpenBSD it's essentially identical with the only difference being the MIB passed in to the sysctl. So basically we could generate the full function body via a macro in generic/ that takes the name of the field to write, the MIB initializer and be done with it. The field to write is also interesting, as for at least DragonFly, FreeBSD and NetBSD the *BSDProcessList_updateExe function is essentially the same, also just differing in the MIB being passed.

[fasterit]

Tested on MacOS as requested. Builds and works fine.

[natoscott]

@BenBE LGTM too