…trip`

rust-lang/rust#90058 stabilized `-Z strip` as
`-C strip`. Stabilize the corresponding Cargo option.

Update the documentation to move it from the unstable reference to the
profiles documentation.

Update the tests to account for stabilization, but make them no-ops on
stable/beta for now until rustc 1.58 releases.

Co-authored-by: Eric Huss <eric@huss.org>