Support IValue string type (#26517)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26517
Support IValue string kind
added 2 instrumented tests -> regenerated test.pt
# Test plan
Start android emulator
```
cd ./android/
gradle pytorch_android:cAT
```
tests passed
# Nits
Moved method IValue#getBool() - to have an order: bool, long, double, string
Test Plan: Imported from OSS
Differential Revision: D17513683
Pulled By: IvanKobzarev
fbshipit-source-id: d328f25772b61f54fb6fd3b2afacde3d7372f25c
