Split packages into "building python" vs "building user packages" (#7877

)

1. Reorder the list of package lexicographically
2. Assume the only packages needed for `pyenv` to install `python` are
   the ones listed in https://github.com/pyenv/pyenv/wiki#suggested-build-environment
3. Move the remaining packages to a separate section of packages that
   are installed in the final image, not the builder image (they're not
   needed for building the various python's)
4. Go through the list of packages that are _potentially_ used for user
   packages, and search the repo issues/PR's/commit log for any
   mentions. Also google to see if any common python libraries require
   them. If so, document why.
5. Delete the remaining packages, they're probably not needed.

This should slightly shrink our build times/image size, but there is a
risk that one or more of the removed libraries are actually needed. If
so, we'll probably see it in Sentry error logs once we deploy and jobs
start running against user repos, and then we can re-add the ones that
are still needed, except this time we'll actually be able to document
_why_ they're needed.

I was a little surprised how many packages I was able to delete... some
of them may be part of the existing base image, but many of them looked
like things that may have been needed for other parts of the monolithic
docker image, but are no longer needed for just the Python bits.

python/Dockerfile

@@ -14,36 +14,24 @@ ARG PY_3_8
 ARG PYENV_VERSION
 USER root
 
+# Install *only* the apt packages required for this builder image to build Python.
+# C-libs needed by users to build their Python packages should be installed down below in the final docker image.
 RUN apt-get update \
   && apt-get upgrade -y \
   && apt-get install -y --no-install-recommends \
-    dirmngr \
-    zlib1g-dev \
-    liblzma-dev \
-    libgdbm-dev \
-    bison \
-    tzdata \
-    zip \
-    openssh-client \
     build-essential \
-    make \
-    libpq-dev \
-    libssl-dev \
     libbz2-dev \
     libffi-dev \
+    liblzma-dev \
+    libncursesw5-dev \
     libreadline-dev \
     libsqlite3-dev \
-    libcurl4-openssl-dev \
-    llvm \
-    libncurses5-dev \
-    libncursesw5-dev \
-    libmysqlclient-dev \
-    xz-utils \
-    tk-dev \
+    libssl-dev \
     libxml2-dev \
     libxmlsec1-dev \
-    libgeos-dev \
-    python3-enchant \
+    tk-dev \
+    xz-utils \
+    zlib1g-dev \
   && rm -rf /var/lib/apt/lists/*
 
 COPY --chown=dependabot:dependabot python/helpers /opt/python/helpers
@@ -82,6 +70,21 @@ COPY --from=python-3.10 /usr/local/.pyenv/3.10.tar.gz /usr/local/.pyenv/3.10.tar
 COPY --from=python-3.9 /usr/local/.pyenv/3.9.tar.gz /usr/local/.pyenv/3.9.tar.gz
 COPY --from=python-3.8 /usr/local/.pyenv/3.8.tar.gz /usr/local/.pyenv/3.8.tar.gz
 
+# Install C-libs needed to build users' Python packages. Please document why each package is needed.
+USER root
+RUN apt-get update \
+  && apt-get upgrade -y \
+  && apt-get install -y --no-install-recommends \
+    # Used by pycurl
+    libcurl4-openssl-dev \
+    # Used by mysqlclient
+    libmysqlclient-dev \
+    # Used by psycopg Postgres Client
+    libpq-dev \
+    # Used by python zoneinfo core lib
+    tzdata \
+  && rm -rf /var/lib/apt/lists/*
+
 USER dependabot
 
 COPY --chown=dependabot:dependabot python $DEPENDABOT_HOME/python