Migrate std::floor to sycl::floor in device kernels

[orrangetabby17]

This pull request refactors several SYCL/XPU kernel files to consistently use sycl::floor instead of std::floor or floorf, and introduces the use of the at::opmath_type type trait to improve numerical precision and type safety. These changes standardize floating-point operations across the codebase, which is important for device compatibility and correctness.

Numerical precision and type safety improvements:

• Introduction of at::opmath_type in multiple kernels (e.g., DeformConv2dKernels.cpp, PsRoiPoolKernels.cpp, RoiPoolKernels.cpp, UnaryFractionKernels.cpp, GridSampler.cpp) to ensure that mathematical operations are performed in a type-safe way.

Device compatibility and code consistency:

• Replacement of all uses of std::floor and floorf with sycl::floor in device kernel code, ensuring compatibility with SYCL device execution.

Header and dependency updates:

• Added #include <ATen/OpMathType.h> where necessary to support the new opmath_type usage.

ASM Difference

• No significant difference in the asm-level between sycl::floor and std::floor.

These changes improve the reliability and maintainability of the code on SYCL devices.