Flatpak: Use json2yaml tool for the yaml manifest

So they are more equal and we have a simple way to generate it.

build-aux/flatpak/org.gnome.Nautilus.yml

@@ -1,87 +1,89 @@
+---
 app-id: org.gnome.NautilusDevel
 runtime: org.gnome.Platform
-runtime-version: 3.30
+runtime-version: '3.30'
 sdk: org.gnome.Sdk
 command: nautilus
 tags:
-  - devel
-  - nightly
+- devel
+- development
+- nightly
 desktop-file-name-prefix: "(Development) "
 finish-args:
-  - --share=ipc
-  - --socket=x11
-  - --socket=wayland
-  - --talk-name=org.gnome.OnlineAccounts
-  - --talk-name=org.freedesktop.Tracker1
-  - --filesystem=host
-  - --talk-name=org.gtk.vfs
-  - --talk-name=org.gtk.vfs.*
-  - --filesystem=xdg-run/dconf
-  - --filesystem=~/.config/dconf:ro
-  # Remove to something better for dconf when ready.
-  # See https://github.com/flatpak/flatpak/issues/78
-  - --talk-name=ca.desrt.dconf
-  - --env=DCONF_USER_CONFIG_DIR=.config/dconf
-  - --env=TRACKER_SPARQL_BACKEND=bus
-
+- "--share=ipc"
+- "--socket=x11"
+- "--socket=wayland"
+- "--talk-name=org.gnome.OnlineAccounts"
+- "--talk-name=org.freedesktop.Tracker1"
+- "--filesystem=host"
+- "--talk-name=org.gtk.vfs"
+- "--talk-name=org.gtk.vfs.*"
+- "--filesystem=xdg-run/dconf"
+- "--filesystem=~/.config/dconf:ro"
+- "--talk-name=ca.desrt.dconf"
+- "--env=DCONF_USER_CONFIG_DIR=.config/dconf"
+- "--env=TRACKER_SPARQL_BACKEND=bus"
+build-options:
+  build-args:
+  - "--share=network"
 modules:
-  - name: exiv2
-    buildsystem: cmake
-    build-options:
-      config-opts:
-        - -DCMAKE_INSTALL_PREFIX=/app
-        - -DCMAKE_INSTALL_LIBDIR=/app/lib
-    sources:
-      - type: archive
-        url: https://github.com/Exiv2/exiv2/archive/v0.26.tar.gz
-        sha256: 51cffa8d19d67e1da6c1d0f570a75b8f6c814113367318c2c0407691888c5f01
-
-  - name: gexiv2
-    buildsystem: meson
-    builddir: true
-    build-options:
-      config-opts:
-        - --libdir=/app/lib
-        - -Ddisable-introspection=True
-    sources:
-      - type: git
-        url: https://gitlab.gnome.org/GNOME/gexiv2.git
-        tag: gexiv2-0.10.8
-
-  - name: tracker
-    cleanup:
-      - /bin
-      - /etc
-      - /libexec
-    buildsystem: meson
-    builddir: true
-    build-options:
-      config-opts:
-        - --libdir=lib
-        - -Ddocs=false
-        - -Dfunctional_tests=false
-        - -Djournal=false
-        - -Dnetwork_manager=no
-        - -Dstemmer=no
-        - -Dbash_completion=no
-        - -Dsystemd_user_services=no
-    sources:
-      - type: git
-        url: https://gitlab.gnome.org/GNOME/tracker.git
-
-  - name: gnome-autoar
-    sources:
-      - type: git
-        url: https://gitlab.gnome.org/GNOME/gnome-autoar.git
-        tag: 0.2.3
-
-  - name: nautilus
-    buildsystem: meson
-    builddir: true
-    build-options:
-      config-opts:
-        - --libdir=/app/lib
-        - -Dprofile=development
-    sources:
-      - type: git
-        url: https://gitlab.gnome.org/GNOME/nautilus.git
+- name: gcovr
+  buildsystem: simple
+  build-commands:
+  - "/usr/bin/pip3 --disable-pip-version-check install --prefix=/app --verbose ."
+  sources:
+  - type: git
+    url: https://github.com/gcovr/gcovr
+    tag: '4.1'
+- name: exiv2
+  config-opts:
+  - "-DCMAKE_INSTALL_PREFIX=/app"
+  - "-DCMAKE_INSTALL_LIBDIR=/app/lib"
+  buildsystem: cmake
+  sources:
+  - type: archive
+    url: https://github.com/Exiv2/exiv2/archive/v0.26.tar.gz
+    sha256: 51cffa8d19d67e1da6c1d0f570a75b8f6c814113367318c2c0407691888c5f01
+- name: gexiv2
+  buildsystem: meson
+  builddir: true
+  config-opts:
+  - "--libdir=/app/lib"
+  - "-Ddisable-introspection=True"
+  sources:
+  - type: git
+    url: https://gitlab.gnome.org/GNOME/gexiv2.git
+    tag: gexiv2-0.10.8
+- name: tracker
+  cleanup:
+  - "/bin"
+  - "/etc"
+  - "/libexec"
+  buildsystem: meson
+  builddir: 'true'
+  config-opts:
+  - "--libdir=lib"
+  - "-Ddocs=false"
+  - "-Dfunctional_tests=false"
+  - "-Djournal=false"
+  - "-Dnetwork_manager=no"
+  - "-Dstemmer=no"
+  - "-Dbash_completion=no"
+  - "-Dsystemd_user_services=no"
+  sources:
+  - type: git
+    url: https://gitlab.gnome.org/GNOME/tracker.git
+- name: gnome-autoar
+  sources:
+  - type: git
+    url: https://gitlab.gnome.org/GNOME/gnome-autoar.git
+    tag: 0.2.3
+- buildsystem: meson
+  builddir: true
+  name: nautilus
+  config-opts:
+  - "--libdir=/app/lib"
+  - "-Dprofile=development"
+  sources:
+  - type: git
+    url: https://gitlab.gnome.org/GNOME/nautilus.git