go bindings: benchmark CGo overhead and #cgo noescape/nocallback

[cyphar]

It's not clear to me how slow CGo actually is for our usecase (and this whether #87 is actually justified). We can probably also tag all of our functions #cgo noescape and/or #cgo nocallback once we update to Go 1.24 (https://github.com/golang/go/issues/56378).