From discussions with @jahzielv.
QAing ADE flows:
1. New version of fleetd is pushed to `edge`
2. QA folks can trigger this new workflow and download the generated
`fleetd-base.pkg` and `fleetd-base-manifest.plist`.
3. Host the downloaded files (in `foobar/`) in their ngroks URLs (using
e.g. `go tools ./tools/file-server 8085 foobar/`)
4. Use Fleet's `FLEET_DEV_DOWNLOAD_FLEETDM_URL` to point the Fleet
server to their ngrok URL.
