Add validation and unit tests AffineGrid (#27572)
### Description
<!-- Describe your changes. -->
This pull request improves the robustness and correctness of the
`AffineGrid` operator in ONNX Runtime by adding stricter input
validation and updating the implementation for better type safety. It
also introduces comprehensive unit tests to verify error handling for
invalid inputs.
### Input validation enhancements
* Added explicit checks in `affine_grid.cc` to ensure that the batch
dimension in `size` matches the batch dimension in `theta`, and that
`theta` has the correct shape for both 2D (`[N, 2, 3]`) and 3D (`[N, 3,
4]`) cases. This prevents silent errors due to shape mismatches.
[[1]](diffhunk://#diff-be745903b4daaa5f01d8cf60477899d19d712d88fad2e9b923f0ab3ec36c1c67L116-R126)
[[2]](diffhunk://#diff-be745903b4daaa5f01d8cf60477899d19d712d88fad2e9b923f0ab3ec36c1c67L131-R147)
### Type safety and code clarity improvements
* Updated grid generation functions to use the template type `T` for
Eigen vector creation, replacing hardcoded `float` types. This ensures
correct behavior for different data types and improves code clarity.
[[1]](diffhunk://#diff-be745903b4daaa5f01d8cf60477899d19d712d88fad2e9b923f0ab3ec36c1c67L31-R36)
[[2]](diffhunk://#diff-be745903b4daaa5f01d8cf60477899d19d712d88fad2e9b923f0ab3ec36c1c67L50-R60)
* Added clarifying comments to matrix and array initializations in
affine grid generator functions to make the code easier to understand
and maintain.
### Test coverage improvements
* Added a series of unit tests in `affine_grid_test.cc` to validate
input shape checks, including cases for incorrect tensor dimensions,
mismatched batch sizes, and invalid `size` lengths. These tests ensure
that the operator fails gracefully with informative error messages when
given invalid inputs.
* Ensured the required test utility header is included to support new
tests.
### Code cleanup
* Removed unused includes from `affine_grid.cc` to tidy up the codebase.
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
