gdbus-codegen: Add missing nullable and optional g-i annotations to generated code

Fixes #1615
15 jobs for <span class="ref-name">wip/1615-gdbus-codgen-nullable</span> in 19 minutes and 35 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #165527
cross-android_api21_arm64

00:00:56

passed #165528
cross-android_api28_arm64

00:08:08

passed #165529
cross-mingw64

00:01:18

passed #166604
fedora-autotools-x86_64

00:05:11

passed #166605
fedora-x86_64

00:06:17

failed #171620
freebsd-11
freebsd-11-x86_64

00:04:35

passed #165530
win32
msys2-mingw32

00:08:34

passed #165531
win32
vs2017-x64

00:07:46

failed #165526
fedora-autotools-x86_64

00:10:51

failed #165525
fedora-x86_64

00:10:52

failed #169376
freebsd-11
freebsd-11-x86_64

00:04:26

failed #168128
freebsd-11
freebsd-11-x86_64

00:04:27

failed #166606
freebsd-11
freebsd-11-x86_64

00:04:15

failed #165532
freebsd-11
freebsd-11-x86_64

00:04:43

 
  Coverage
skipped #165533
coverage
 
Name Stage Failure
failed
freebsd-11-x86_64 Build
TIMEOUT:    0

Full log written to /var/tmp/gitlab_runner/builds/3fe11159/0/GNOME/glib/_build/meson-logs/testlog.txt
Uploading artifacts...
_build/config.h: found 1 matching files
_build/glib/glibconfig.h: found 1 matching files
_build/meson-logs: found 4 matching files
Uploading artifacts to coordinator... ok id=171620 responseStatus=201 Created token=8bzSodRx
ERROR: Job failed: exit status 1