Add Python in dockerfiles (#890)

Author: tpadioleau

docker/latest/Dockerfile

@@ -52,6 +52,7 @@ RUN chmod +x /bin/bash_run \
     libhwloc-dev \
     pkg-config \
     pipx \
+    python3 \
  && python3 -m pipx install gcovr \
  && python3 -m pipx ensurepath \
  # Installing cmake < 3.28 to workaround issue with Kokkos

docker/oldest/Dockerfile

@@ -51,6 +51,7 @@ RUN chmod +x /bin/bash_run \
     liblapacke-dev \
     libhwloc-dev \
     pkg-config \
+    python3 \
  && case "${BACKEND}" in \
     "cpu") \
       apt-get install -y --no-install-recommends \