ci: windows dockerfile used by Jenkins can override image

Author: henryborchers

vars/runJenkinsPipeline.groovy

@@ -510,7 +510,7 @@ def call(){
                                             script{
                                                 def envs = []
                                                 node('docker && windows'){
-                                                    docker.image('python').inside("--mount type=volume,source=uv_python_install_dir,target=${env.UV_PYTHON_INSTALL_DIR}"){
+                                                    docker.image(env.DEFAULT_PYTHON_DOCKER_IMAGE ? env.DEFAULT_PYTHON_DOCKER_IMAGE: 'python').inside("--mount type=volume,source=uv_python_install_dir,target=${env.UV_PYTHON_INSTALL_DIR}"){
                                                         try{
                                                             checkout scm
                                                             bat(script: 'python -m venv venv && venv\\Scripts\\pip install --disable-pip-version-check uv')
@@ -537,7 +537,7 @@ def call(){
                                                             "Tox Environment: ${toxEnv}",
                                                             {
                                                                 node('docker && windows'){
-                                                                    docker.image('python').inside("--mount type=volume,source=uv_python_install_dir,target=${env.UV_PYTHON_INSTALL_DIR}"){
+                                                                    docker.image(env.DEFAULT_PYTHON_DOCKER_IMAGE ? env.DEFAULT_PYTHON_DOCKER_IMAGE: 'python').inside("--mount type=volume,source=uv_python_install_dir,target=${env.UV_PYTHON_INSTALL_DIR}"){
                                                                         checkout scm
                                                                         try{
                                                                             retry(3){
@@ -680,7 +680,7 @@ def call(){
                                                     checkout scm
                                                     unstash 'PYTHON_PACKAGES'
                                                     if(['linux', 'windows'].contains(entry.OS) && params.containsKey("INCLUDE_${entry.OS}-${entry.ARCHITECTURE}".toUpperCase()) && params["INCLUDE_${entry.OS}-${entry.ARCHITECTURE}".toUpperCase()]){
-                                                        docker.image('python').inside(isUnix() ? '': "--mount type=volume,source=uv_python_install_dir,target=C:\\Users\\ContainerUser\\Documents\\uvpython"){
+                                                        docker.image(env.DEFAULT_PYTHON_DOCKER_IMAGE ? env.DEFAULT_PYTHON_DOCKER_IMAGE: 'python').inside(isUnix() ? '': "--mount type=volume,source=uv_python_install_dir,target=C:\\Users\\ContainerUser\\Documents\\uvpython"){
                                                              if(isUnix()){
                                                                 withEnv([
                                                                     'PIP_CACHE_DIR=/tmp/pipcache',