[$] Kernel time APIs for Rust

While the 6.3 kernel has gained more support for the Rust language, it
still remains true that there is little that can be done in Rust beyond the
creation of a "hello world" module. That functionality was already
available in C, of course, with a level of safety similar to what Rust can
provide. Interest is growing, though, in merging actually useful modules
written in Rust; that will require some more capable infrastructure than is
currently present. A recent discussion on the handling of time values in
Rust demonstrates the challenges — and opportunities — inherent in this
effort.