`pprof::symbolize()` used a regex to strip the Rust monomorphization
suffix from generic methods. However, the `backtrace` crate can do this
itself if formatted with the `:#` flag.
Also tighten up the code a bit.
Avoids compiling the crate and its dependencies into binaries that don't
need them. Shrinks the compute_ctl binary from about 31MB to 28MB in the
release-line-debug-size-lto profile.