Upgrade cryptography to 3.4.6 (#8730)

* Upgrade cryptography to 3.4.6

* Fix comment with instructions for how to use hashin

* run tools/rebuild_certbot_constraints.py

* add deps for building cryptography in snaps

* Update cryptography build dependencies for docker

* Update sources for test farm tests

* Remove rust if it's installed for test farm tests

* source bootstrap script and call sudo as needed

snap/snapcraft.yaml

@@ -70,7 +70,15 @@ parts:
       - python3-pkg-resources
       - python3.8-minimal
     # To build cryptography and cffi if needed
-    build-packages: [gcc, libffi-dev, libssl-dev, git, libaugeas-dev, python3-dev]
+    build-packages:
+      - gcc
+      - git
+      - libaugeas-dev
+      - build-essential
+      - libssl-dev
+      - libffi-dev
+      - python3-dev
+      - cargo
     build-environment:
       - SNAPCRAFT_PYTHON_VENV_ARGS: --upgrade
       # Constraints are passed through the environment variable PIP_CONSTRAINTS instead of using the