Fix doxygen issues (#28122)
This pull request makes several documentation improvements and
clarifications to the ONNX Runtime C API header files. The changes focus
on improving the accuracy and consistency of API references, especially
for function and ownership documentation, and on enhancing Doxygen group
annotations.
**Documentation and API Reference Improvements:**
* Updated references to function names in documentation comments to use
the correct qualified names (e.g., `OrtApi::GetTensorTypeAndShape`
instead of `::GetTensorTypeAndShape`) for clarity and consistency.
* Improved documentation for kernel ownership and release by referencing
methods via `OrtEpApi` (e.g., `OrtEpApi::ReleaseKernelImpl` and
`OrtEpApi::KernelRegistry_AddKernel`) instead of global functions,
ensuring the documentation matches the API design.
[[1]](diffhunk://#diff-2d8e6d37bb0ef428daa560918f0fc5e9de31ff9eb5b66f857fed0769bebccb80L1555-R1560)
[[2]](diffhunk://#diff-2d8e6d37bb0ef428daa560918f0fc5e9de31ff9eb5b66f857fed0769bebccb80L1591-R1596)
[[3]](diffhunk://#diff-2d8e6d37bb0ef428daa560918f0fc5e9de31ff9eb5b66f857fed0769bebccb80L1623-R1628)
**Doxygen Group Annotation Enhancements:**
* Added and corrected Doxygen group annotations (`\addtogroup Global`
and `@}`) in `onnxruntime_ep_c_api.h` to properly group related API
declarations, improving generated documentation structure.
[[1]](diffhunk://#diff-2d8e6d37bb0ef428daa560918f0fc5e9de31ff9eb5b66f857fed0769bebccb80R17-R19)
[[2]](diffhunk://#diff-2d8e6d37bb0ef428daa560918f0fc5e9de31ff9eb5b66f857fed0769bebccb80R36)
**Minor Cleanup:**
* Removed an extraneous documentation group annotation to maintain
proper Doxygen formatting.
