Automatically fetch the GNSS assistance data from the Web
to heavily reduce the time to acquire a GNSS lock by uploading
the assistance data to the modem.
This feature is optional and can be disabled in the configuration
as people may prefer to not download the assistance data from
the Quectel/Qualcomm servers.
Also configure the GNSS engine to optimize the performance
and power consumption.
This commit prepares the use of device-specific configuration files.
These files should be named after the device-tree `compatible` string
with the `toml` extension.
`eg25-manager` will search for config files in
`<prefix>/etc/eg25-manager` first (or `/etc/eg25-manager` if prefix is
`/usr`), then in `<prefix>/share/eg25-manager`.
Most of the modem issues follow a (incomplete) USB device reset. Instead
of relying solely on the existing timer, this patch adds a udev monitor
which resets the modem as soon as its associated USB device is reset,
which greatly improves recovery time.
