settings: Adjust event name base on notifcations category

Adjust the emitted feedback based on the notifaction category¹. We could
use the sound-name instead or invent x-phosh-event-name (and might even
add support for that later on) but that has the problem that the
application sometimes has a hard time to figure out what the appropriate
event is. E.g. `message-missed-instant` and `message-new-instant` are
hard to tell apart from an application PoV.

1: https://specifications.freedesktop.org/notification-spec/notification-spec-latest.html

Signed-off-by: Guido Günther <guido.gunther@puri.sm>
9 jobs for notification-event-type in 49 minutes and 51 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #359852
librem5
build:cross-debian-bullseye:i386

00:16:23

passed #359853
librem5
build:native-alpinelinux-edge

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passed #359851
librem5
build:native-debian-bullseye

00:16:33

 
  Test+Docs
passed #359855
librem5
build-gtkdoc

00:12:31

passed #359857
librem5
check-license-headers

00:02:38

passed #359856
librem5
check-po

00:00:26

passed #359858
librem5
unit-test:native-alpinelinux-edge

00:00:52

passed #359854
librem5
unit-test:native-debian-bullseye

00:14:07

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  Package
passed #359859
librem5:arm64
package:deb-pureos-byzantium:arm64

00:19:09