legion_prof_rs: Update Cargo metadata for release and upgrade dependencies

This MR sets us up to be able to publish Legion Prof on crates.io, the official platform for Rust packages.

• From now on, the profiler will be versioned in sync with Legion releases. A Legion version YY.MM.A will become Legion Prof version 0.YYMM.A. Note the leading zero, and the lack of a dot between YYMM in the second component of Legion Prof. This is necessary to be compatible with semver.
• We are switching to the officially published legion_prof_viewer crate at: https://crates.io/crates/legion_prof_viewer
• Other metadata has been provided as required for an official release.