[pkg] use plugs in snap

with this we can get rid of ugly hack that got gtk environment inside
the snap manually, and forced us to stage libc6 into the snap because of
linker incompatibility problems.

seems whatever problem made me go that way is already solved by snap.

branding/templates/snap/snapcraft-template.yaml

@@ -7,25 +7,11 @@ description: |
         any way. The service is paid for entirely by donations from users like you.
 grade: stable
 confinement: classic
-icon: snap/gui/icon.svg
+icon: icon.svg 
 base: core18
 
 parts:
-        desktop-gtk3:
-                plugin: nil
-                stage-packages:
-                    - libc6
-                prime:
-                    - '*'
-                    - -usr/include
-                    - -usr/lib/locale
-                    - -usr/share/X11/locale
-                    - -usr/share/doc
-                    - -usr/share/locale
-                    - -usr/share/man
-         
         bitmask-root:
-                after: [desktop-gtk3]
                 plugin: dump
                 source: ../../helpers/
                 override-prime: |
@@ -37,20 +23,19 @@ parts:
                 plugin: nil
                 stage-packages:
                     - openvpn
-                    - libc6
                 prime:
                     - -usr/share/doc
                     - -usr/share/man
 
         bitmask-vpn:
-                after: [desktop-gtk3]
                 plugin: go
                 source: ../../cmd/bitmask-vpn
                 go-importpath: 0xacab.org/leap/bitmask-vpn/cmd/bitmask-vpn
                 go-packages:
                         - 0xacab.org/leap/bitmask-vpn/cmd/bitmask-vpn
                 override-build: |
-                      cp $SNAPCRAFT_STAGE/../snap/local/${binaryName}.desktop $SNAPCRAFT_PRIME/${binaryName}.desktop
+                      mkdir -p $SNAPCRAFT_PRIME/usr/share/applications
+                      cp $SNAPCRAFT_STAGE/../snap/local/${binaryName}.desktop $SNAPCRAFT_PRIME/usr/share/applications/${binaryName}.desktop
                       snapcraftctl build
                 override-prime: |
                       rm -rf $SNAPCRAFT_PRIME/../snap/hooks/.mypy_cache
@@ -62,7 +47,6 @@ parts:
                     - libappindicator3-dev
                     - libgtk-3-dev
                 stage-packages:
-                    - libc6
                     - libpcre3
                     - libappindicator3-1
                     - zlib1g
@@ -70,9 +54,18 @@ parts:
 apps:
         launcher:
                 command: bin/bitmask-vpn
-                desktop: ${binaryName}.desktop
+                command-chain: [snap/command-chain/desktop-launch]
+                desktop: usr/share/applications/${binaryName}.desktop
                 environment:
                         LD_LIBRARY_PATH: "$SNAP/usr/lib/$(gcc -print-multiarch):$SNAP/lib/$(gcc -print-multiarch):$LD_LIBRARY_PATH"
+                plugs:
+                    - desktop
+                    - desktop-legacy
+                    - home
+                    - network
+                    - unity7
+                    - wayland
+                    - x11
         openvpn:
                 command: usr/sbin/openvpn
         bitmask-root: