Update Eigen to the latest (#23717)
#### Changes related to Eigen:
1. **Update eigen.cmake**: Removed the use of cmake's
`fetchcontent_populate` command as it is deprecated.
2. **Upgrade Eigen**: Updated Eigen to the latest version to resolve a
build issue. Without this update, the Android build would check for a
Fortran compiler and report an error when running cmake config in
Eigen's source directory.
3. **Add Eigen as a vcpkg port**: Added Eigen as a vcpkg port since the
official vcpkg repository version is outdated.
4. **Remove eigen_INCLUDE_DIRS variable**: Removed the
`eigen_INCLUDE_DIRS` cmake variable and replaced it with
`Eigen3::Eigen`.
This change enables building ONNX Runtime(CPU EP only) as a vcpkg port.
To do so, you also need to download the
ports/onnxruntime/vcpkg.json file from this PR:
https://github.com/microsoft/vcpkg/pull/36850
