Fix choice branch selection per errata 5.60

- Update unparser choice branch selection to match errata 5.60: prefer the first branch fully defaultable/OVC/optional instead of the first empty one.
- Make required arrays return `true` for `isRequiredStreamingUnparserEvent` for consistency with defaulting behavior.
- Add subset error when arrays with required elements have default values.
- Rename `canUnparseIfHidden` for clarity—it isn’t limited to hidden elements.
- Mark required but empty arrays as `PossiblyZeroArrayOccurrencesDetector` to suppress separators.
- Simplify `optDefaultBranch` logic: `canUnparseIfNoEvents` subsumes `isOpen`/`isEmpty`.
- Remove `MultipleChoiceBranches` warning—multiple valid defaults are allowed.
- In `pneResolver`, handle arrays using `possibleSelfPlusNextLexicalSiblingStreamingUnparserElements`.
- For complex elements, check both element and member requiredness for unparse eligibility.
- Update CLIDebugger test schema to cover suspension cases.
- Disallow hidden IVCs except in unselected choice branches; require IVCs in the infoset.
- Remove support for hidden IVCs in sequences and add tests confirming hidden IVCs aren’t selected by `optDefaultBranch`.

Discussion
Hidden IVCs are elements computed during parse but never represented in the
  infoset or needed during unparse. They are not meaningful for unparsing and
  should not be supported. So we remove !e.isRepresented from the ElementBase
  case. Unparsing should instead require IVC elements (minOccurs = maxOccurs = 1)
  to appear in the infoset, even though their values are ignored at unparse
  time. This behavior is more intuitive and is in line with IVC being MustExist in
  unparserInfosetElementDefaultingBehavior and preserves expected branch selection semantics for
  choice/dispatch constructs. Hidden IVCs remain permissible only within choice branches that
  are not selected during unparse. Note that we will never select a default branch with a Hidden
  IVC because it will always be canUnparseIfNoEvents=false

Deprecation/Compatibility
Per DFDL errata 5.60, the first branch that can be unparsed entirely without any infoset events (i.e. made up of elements that are dfdl:outputValueCalc, option branches, zero length arrays, or defaultable elements) in a choice is selected, rather than prioritizing the first empty branch. Also, required arrays are no longer treated as optional and hidden IVCs are only permissible in choices.

DAFFODIL-2324