Adapt https://github.com/aya-rs/aya/commit/3d463a3 and subsequent work
to the template. This has worked very well for us in the main project,
and our users should get the same hotness.
Note that xtask is still used for running, as it is in the main project.
structopt was merged into clap (starting from clap 3.0), therefore
becoming a deprecated project.
Signed-off-by: Michal Rostecki <vadorovsky@gmail.com>