Cleanup: replace stack of `operationsTracker` in `LazyTensorContext` into a single tracker. (#382)
Cleanup: replace stack of `operationsTracker` in `LazyTensorContext` into a single tracker. (#382)

* Change operationsTracker in `LazyTensorContext` to a single tracker.

* Remove _ from private operationsTracker.

tensorflow/swift-apis,tensorflow/swift-apis,tensorflow/swift-apis,tensorflow/swift-apis,tensorflow/swift-apis