Add testId support to picker items

[LoserAntbear]

Is your feature request related to a problem? Please describe.

Picker itself provide testId support, but items do not have it. For the sake of improvement of testing of the components testId support should be added.

Describe the solution you'd like

A testId prop should be added to the item in renderer method. Interestingly,PickerItem component already has it, but renderItem method does not propagate it.

Describe alternatives you've considered

For now the easies solution is a monkeypatch, but it's the last resort.

Additional details

Missing prop propagation

Proof of support of testID prop by Item component

[LoserAntbear]

I'd like to commit to this, if approved.

[lfkwtz]

#498