Add some missing type libraries for mypy (#9657)

* add some missing types

* install pkg-config

* install pkg-config for docker too

* add pkg-config to plugins

* pkg-config when cryptography may need to be built

* deps cleanup

* more comments

* more tweaks

snap/snapcraft.yaml

@@ -79,6 +79,7 @@ parts:
       - libffi-dev
       - python3-dev
       - cargo
+      - pkg-config
     build-environment:
       # We set this environment variable while building to try and increase the
       # stability of fetching the rust crates needed to build the cryptography