[LTC] Tweak LazyTensor Class for XLATensor (#90363)
Summary:
This pull request makes some tweaks on LazyTensor class such that it's easier for XLATensor to inherit.
1. It replaces data_ptr() with data() which now returns a const shared_ptr& type.
2. It adds a temporary ctor to LazyTensor::Data such that XLATensor::Data can easily inherits it.
3. It moves LazyTensor(std::shared_ptr<Data>) and SetTensorData(at::Tensor) to protected for XLATensor to access.
Test Plan:
CI.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/90363
Approved by: https://github.com/JackCaoG
