[LTC] Restore default ctor for LazyTensor (#90086)
Summary:
This pull request introduced a temporarily change that make XLA's LTC migration easier. One step among is to make XLATensor naively inherits LazyTensor and that requires LazyTensor to have a default constructor.
Test Plan:
CI.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/90086
Approved by: https://github.com/JackCaoG, https://github.com/kit1980
