[FEATURE] Convert distillery release to executable

[brooksmtownsend]

Is your feature request related to a problem? Please describe. The current install / run process of wasmcloud is a little clunky, download a tarball, extract, then run ./bin/wasmcloud_host wherever it's extracted to.

Describe the solution you'd like With the --executable flag, distillery supports creating a self-extracting tarball that will extract and execute all in one command. The run process would then be

1. Download the --wasmcloud script (it's shown as a POSIX shell script, but works the same on different machines)
2. Move that script to your path, calling it wasmcloud
3. Run wasmcloud foreground (still need to examine if this will work in /usr/local/bin, it extracts the host files under a tmp directory

This will greatly simplify the download, install, and run process for those not used to elixir releases, as well as our documentation.