Remove usages of Default on windows

[chelsea0x3b]

Resolves #469

[gemini-code-assist]

Code Review

This pull request removes the usage of ..Default::default() for initializing CUDA handle description structs on Windows, replacing it with explicit field initialization. This is a good change for explicitness and safety, especially since the Default implementation might not be reliable across all platforms.

The change in src/driver/result.rs is correct. However, the change in src/runtime/result.rs is incomplete. It misses the conditional initialization of the reserved field for the cuda-13000 feature, which is present in the unix counterpart. I've added a critical comment to address this to prevent compilation errors.

[gemini-code-assist]

The reserved field is missing here. The unix version of this function, import_external_memory_opaque_fd, conditionally includes the reserved field for cuda-13000. To ensure consistency and prevent compilation errors when the cuda-13000 feature is enabled, you should also include the reserved field here under the same conditional compilation flag.

            flags: 0,
            #[cfg(feature = "cuda-13000")]
            reserved: [0; 16],