SelectableText is currently a read only EditableText which has several issues, such as the selection is bounded in a single selectable text, and it may be costly in terms of memory usage.

The idea is reimplement SelectableText with SelectionArea + text, but we should make sure they are feature on par before we do that.

several issue with SelectionArea:

#111370
#111021 （fixed）
#110594 (won't fix)
#104703 (fixed)
#104603 (fixed)
#104594
#126652 (fixed)