Rollup merge of #150288 - offload-bench-fix, r=ZuseZ4

Add scalar support for offload

This PR adds scalar support to the offload feature. The scalar management has two main parts:

On the host side, each scalar arg is casted to `ix` type, zero extended to `i64` and passed to the kernel like that.
On the device, the each scalar arg (`i64` at that point), is truncated to `ix` and then casted to the original type.

r? @ZuseZ4

Author: Zalathar