Fix missing DC value in some check context flags

[In3luki]

When context.dc is a StatisticDifficultyClass, the DC value is a getter and is therefore non-enumerable, causing it to be dropped by the omit helper.

Closes #21205

[CarlosFdez]

How long is the list of properties we're seeking to pull? Perhaps a pick would be cleaner?

[In3luki]

Looks like picking would work and is indeed cleaner.

{
      dc: context.dc ? R.pick(context.dc, ["label", "scope", "slug", "value", "visible"]) : null,
}

I've looked at a check roll and an attack roll before & after and the flags look the same. The only downside is, that the list of picked properties may need to be updated if the CheckDC properties change.

[CarlosFdez]

Hopefully typescript would take care of that. I just prefer to avoid non-multiple of 4 indentation that prettier likes to add in these situations where possible. Its either that or adding a getTraceData() equivalent that uses that and falls back to the dc.

If I remember right value is a getter because we want to be able to defer its computation, so we can't simply convert that to a variable.

[In3luki]

Yeah, it's probably fine. The dc flag is only used for rerolls in the system and modules can request other hypothetical new properties if they need them.