Adds UNIDIRECTIONAL_SEQUENCE_RNN op

* Changes docs
* Adds tests

Test: NeuralNetworksTest_static
Fix: 113560505
Change-Id: Id179f2e750fe79d53c79991c798ec7fc3f86ffb7
Merged-In: Id179f2e750fe79d53c79991c798ec7fc3f86ffb7
(cherry picked from commit 8a5a3d3736351d4cd010dfbe4ee094e51e33c80b)
12 files changed