This commit adds the `--profiler-trace-path` flag. When combined with `-p` to
enable profiling, it dumps a profile as a self-contained HTML file to the given
path. The profile visualizes the traced operations as a gant-chart style
timeline.
This commit adds a test crate for the time profiler to `tests/unit/profile`. The
only unit test contained in this crate is a smoke test that the time profiler
thread can be created and destroyed. It serves as a place for adding new tests
in the future.
