Motivation:
Calling AbstractCharClass.setNegative always leads to
mayContainSupplCodepoints being `true`, even when `alt` is already
equal to the argument. Given that CharClass always calls setNegative
with its constructor parameter - `negative`, mayContainSupplCodepoints
always gets set. i.e. `[a]` will have mayContainSupplCodepoints set.
mayContainSupplCodepoints affects what node (RangeSet or SupplementaryRangeSet)
wraps this char class. See Pattern.processRangeSet.
RangeSet is better optimized and avoids recursion when it is quantified.
Modification:
Set `mayContainSupplCodepoints` flag only when `alt` is updated.
When `alt` is updated, this char class gets inverted, hence now may
contain supplementary code points.
Otherwise, content of this char class does not change, i.e. no new
supplementary code points is added.
Result:
Fixes KT-46211.
Abduqodiri Qurbonzoda
6e50bbee3b