kdump-load/save-logs: Log submission decoupling / major refactor

This is a pretty big refactor in the logic / goals of this kdump
implementation.

* WHY?

We want to decouple completely the log submission mechanism from the
kdump tooling, for mainly two reasons: reuse this submission API/mechanism
in other log collection tools, and to allow upstreaming the kdump tooling
for Arch Linux generically, not embedding SteamOS particulars to it.

* HOW:

First of all, we dropped the log submission bits from this codebase.
We also deleted the particulars of SteamOS/Deck in the log naming,
like collecting the serial of the device if "Jupiter" model is found
in the DMI info or getting the Steam user account via the VDF file.
All of that will happen in a later stage of the log processing, done by
*another tool* that shall rename the logs and transmit them to the
Valve servers.

While at it, we've done other small changes in the logic to make this
kdump tool more generic and reliable, like allowing the collection
of kdump *AND* pstore logs (not choosing one of them).

* CAVEATS / TODO:

More to come in this front, we still definitely need to remove more
references to SteamOS and clear a bit the code from its particulars.
Important also is to update the README to reflect the changes made
by the upstreaming effort.

Mea culpa: these changes are invasive, switch some logic and
expectations around the package, so making them fully bisectable
would be way harder than not. Hence, please take that into account:
this series should be tested/merged as a whole, it's not guaranteed
that individual patches work correctly in a standalone fashion.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>

kdump.conf

@@ -39,8 +39,3 @@ GRUB_AUTOSET=1
 #  relies in having an available RAM buffer on /proc/iomem with at least 5MiB
 #  in size.
 USE_PSTORE_RAM=1
-
-#  By default, collected logs are submitted automatically to Valve servers.
-#  Setting LOG_SUBMISSION to '0' will disable this behavior; but notice that
-#  even with the log submission disabled, the logs are saved locally.
-LOG_SUBMISSION=1