Add support for SetOfNormalizedString for TextInput

[BenHenning]

See oppia/oppia#10882 for context. We should make these changes on Android, too, though it will require updating our test & production exploration files (the latter of which needs to be done by @rt4914 or myself).

[BenHenning]

@rt4914 might be nice as a SLoP project. It has less details than a second issue, and is therefore more targeted for more established contributors that can figure this out from the reference PR.

[anandwana001]

@rt4914 could you please confirm if this is similar - #3200

[rt4914]

Looks similar.

[BenHenning]

This was fixed in #3796.