gdbus-codegen: add autocleanup for FooObject

This is only enabled with `--c-generate-autocleanup all` for the
reasons discussed on https://bugzilla.gnome.org/show_bug.cgi?id=763379.
9 jobs for <span class="ref-name">wjt/gdbus-codegen-add-autocleanup-for-FooObject</span> in 23 minutes and 38 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Build
passed #135308
cross-android_api21_arm64

00:01:00

passed #135309
cross-android_api28_arm64

00:00:56

passed #135310
cross-mingw64

00:01:30

passed #135307
fedora-autotools-x86_64

00:04:30

passed #135306
fedora-x86_64

00:06:31

passed #135313
freebsd-11
freebsd-11-x86_64

00:04:26

passed #135311
win32
msys2-mingw32

00:08:15

passed #135312
win32
vs2017-x64

00:07:27

 
  Coverage
passed #135314
coverage

00:02:04

75.1%