Always "pipstrap" when running pip_install.py (#9658)

Fixes https://github.com/certbot/certbot/issues/7921.

In all cases when we run `pip_install.py`, we first run `pipstrap.py`. This PR combines these two steps for convenience and to make always doing that less error prone. This will also help me with some of the `tox.ini` refactoring I'm planning to do.

I ran the full test suite on everything and tested the release script changes locally.

This change shouldn't have any effect on cryptography's setup because they install `certbot[test]` which depends on pip, setuptools, and wheel.

* always pipstrap

* use pip_install.py during releases

.azure-pipelines/templates/jobs/packaging-jobs.yml

@@ -62,7 +62,6 @@ jobs:
           addToPath: true
       - script: |
           python -m venv venv
-          venv\Scripts\python tools\pipstrap.py
           venv\Scripts\python tools\pip_install.py -e windows-installer
         displayName: Prepare Windows installer build environment
       - script: |
@@ -99,7 +98,6 @@ jobs:
         displayName: Retrieve Windows installer
       - script: |
           python -m venv venv
-          venv\Scripts\python tools\pipstrap.py
           venv\Scripts\python tools\pip_install.py -e certbot-ci
         env:
           PIP_NO_BUILD_ISOLATION: no
@@ -171,7 +169,6 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y --no-install-recommends nginx-light snapd
           python3 -m venv venv
-          venv/bin/python tools/pipstrap.py
           venv/bin/python tools/pip_install.py -U tox
         displayName: Install dependencies
       - task: DownloadPipelineArtifact@2
@@ -209,7 +206,6 @@ jobs:
       - script: |
           set -e
           python3 -m venv venv
-          venv/bin/python tools/pipstrap.py
           venv/bin/python tools/pip_install.py -e certbot-ci
         displayName: Prepare Certbot-CI
       - script: |

.azure-pipelines/templates/steps/tox-steps.yml

@@ -30,7 +30,6 @@ steps:
       addToPath: true
   - bash: |
       set -e
-      python3 tools/pipstrap.py
       python3 tools/pip_install.py tox
     displayName: Install runtime dependencies
   - task: DownloadSecureFile@1