Replace gzip with zstd for speed + size benefits

Replace `gzip` with `zstd` for both speed + size benefits.

I added `zstd` to the base image rather than the python-specific image
because:
1. it's only 1,695 KB
2. We'll likely use it in other places down the road, such as unpacking deps for jobs
3. The Python image would have required additional steps like `apt-get
   update`

This results in faster compression + space savings:
```shell
root@ca684869d4af:/usr/local/.pyenv/versions# time tar -acf 3.11.5.tar.gz 3.11.5

real	0m5.564s
user	0m5.458s
sys	0m0.626s
root@ca684869d4af:/usr/local/.pyenv/versions# time tar -acf 3.11.5.tar.zst 3.11.5

real	0m0.850s
user	0m1.003s
sys	0m0.354s
root@ca684869d4af:/usr/local/.pyenv/versions# ls -lah
-rw-r--r-- 1 root       root        32M Sep  1 17:19 3.11.5.tar.gz
-rw-r--r-- 1 root       root        30M Sep  1 17:20 3.11.5.tar.zst
```

As well as faster decompression too:
```shell
root@ca684869d4af:/usr/local/.pyenv/versions# ls -lah
-rw-r--r-- 1 root       root        32M Sep  1 17:38 3.11.5.tar.gz
-rw-r--r-- 1 root       root        30M Sep  1 17:36 3.11.5.tar.zst
root@ca684869d4af:/usr/local/.pyenv/versions# time tar -axf $PYENV_ROOT/versions/3.11.5.tar.gz -C $PYENV_ROOT/versions

real	0m1.113s
user	0m0.986s
sys	0m0.811s
root@ca684869d4af:/usr/local/.pyenv/versions# rm -rf 3.11.5
root@ca684869d4af:/usr/local/.pyenv/versions# time tar -axf $PYENV_ROOT/versions/3.11.5.tar.zst -C $PYENV_ROOT/versions

real	0m0.774s
user	0m0.501s
sys	0m0.695s
```

The `-a` flag to `tar` tells it to autoselect the compression format
based on the file extension, so it's flipping between `gzip` and `zstd`.

Dockerfile.updater-core

@@ -14,9 +14,11 @@ RUN apt-get update \
     # dev dependencies for CI
     build-essential \
     curl \
-    zlib1g-dev \
     libgmp-dev \
+    # Compression libs
+    zlib1g-dev \
     unzip \
+    zstd \
     # VCS section
     git \
     git-lfs \

python/Dockerfile

@@ -48,7 +48,7 @@ RUN PYENV_VERSION=$PY_3_8 pyenv exec python --version | grep "Python $PY_3_8" ||
 RUN bash /opt/python/helpers/build $PY_3_8
 # This python environment occupies ~0.5 GB and gets used for a fraction of jobs, so store it compressed.
 RUN cd $PYENV_ROOT/versions \
-  && tar czf $PY_3_8.tar.gz $PY_3_8
+  && tar -acf $PY_3_8.tar.zst $PY_3_8
 
 ## 3.9
 # Docker doesn't support parametrizing `COPY --from:python:$PY_1_23-bookworm`, so work around it using an alias.
@@ -66,7 +66,7 @@ RUN PYENV_VERSION=$PY_3_9 pyenv exec python --version | grep "Python $PY_3_9" ||
 RUN bash /opt/python/helpers/build $PY_3_9
 # This python environment occupies ~0.5 GB and gets used for a fraction of jobs, so store it compressed.
 RUN cd $PYENV_ROOT/versions \
-  && tar czf $PY_3_9.tar.gz $PY_3_9
+  && tar -acf $PY_3_9.tar.zst $PY_3_9
 
 ## 3.10
 # Docker doesn't support parametrizing `COPY --from:python:$PY_1_23-bookworm`, so work around it using an alias.
@@ -84,7 +84,7 @@ RUN PYENV_VERSION=$PY_3_10 pyenv exec python --version | grep "Python $PY_3_10"
 RUN bash /opt/python/helpers/build $PY_3_10
 # This python environment occupies ~0.5 GB and gets used for a fraction of jobs, so store it compressed.
 RUN cd $PYENV_ROOT/versions \
-  && tar czf $PY_3_10.tar.gz $PY_3_10
+  && tar -acf $PY_3_10.tar.zst $PY_3_10
 
 ## 3.11
 # Docker doesn't support parametrizing `COPY --from:python:$PY_1_23-bookworm`, so work around it using an alias.

python/lib/dependabot/python/language_version_manager.rb

@@ -23,7 +23,7 @@ def install_required_python
         return if SharedHelpers.run_shell_command("pyenv versions").include?(" #{python_major_minor}.")
 
         SharedHelpers.run_shell_command(
-          "tar xzf /usr/local/.pyenv/versions/#{python_version}.tar.gz -C /usr/local/.pyenv/versions"
+          "tar -axf $PYENV_ROOT/versions/#{python_version}.tar.gz -C $PYENV_ROOT/versions"
         )
       end