I don't know. It seems fairly common to use std::panic::catch_unwind as a top-level error handler. compiler/rustc_driver_impl/src/lib.rs has this:

    /// The compiler currently unwinds with a special sentinel value to abort
    /// compilation on fatal errors. This function catches that sentinel and turns
    /// the panic into a `Result` instead.

That's clearly using unwinding as a control flow primitive.

There's another example in src/tools/rustfmt/src/lib.rs, in format_snippet, where panics apparently are just suppressed.

I expect application servers for Rust to handle panics in a similar way: abort a specific request, but not terminate the whole process.