fixes #25419; lift magic types to typeclasses

[Copilot]

Reviewed PR changes that prevent compilation errors when user-defined procedures shadow magic type names like seq, array, etc.

Changes

• Added tyUncheckedArray to the set of magic types {tySet, tyArray, tySequence} that are lifted to tyBuiltInTypeClass when their element type is tyNone
• Used elementType accessor for cleaner type child access
• tyOpenArray and tyVarargs remain excluded (special-cased at line 1657 to not receive tyNone children)

Example

type
  TRedisList* = seq[TListItem]

# This proc now won't break the type alias above
proc seq*() =
  discard

The fix ensures magic generics are properly represented as typeclasses during semantic analysis, preventing shadowing conflicts.

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