Extend OrtAllocator API to get Allocator statistics (#24785)
### Description
<!-- Describe your changes. -->
Extend IAllocator to get Allocator statistics:
- Add `OrtAllocator::GetStats` and `AllocatorGetStats` C-API.
- Add `Ort::Allocator::GetStats` Cxx API to parse the string and return
as map.
- Add UT.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Our system integrates multiple models for inference, each with varying
memory demands. Providing a mechanism to retrieve detailed memory
statistics would be useful for analyzing memory usage across models and
devices more effectively.