vdk-quickstart: remove use of global varaibles in CI

The use of global variables in GitLab CI can create problems when
multiple CI files are being imported, as variables are not scoped to a
specific file. This can lead to unexpected variables being set, causing
issues in the CI/CD pipeline.

This is what is happening wiht quickstart-vdk test -
https://gitlab.com/vmware-analytics/versatile-data-kit/-/jobs/3901914540

It expected that there's python installed because it's supposed to use
python image but some other file overrides this image to docker and
causes the test to fail.

This changes quickstart-vdk to use job-level variables.

In future changes I will be changing all CIs to use  job-level variables
or environment variables to avoid conflicts and ensure proper scoping.
Or ensure that global variabels and labels are prefixed with the project
or plugin name.

Testing Done: this PR CI

Signed-off-by: Antoni Ivanov <[email protected]>

projects/vdk-plugins/.plugin-common.yml

@@ -51,6 +51,7 @@
   extends: .build-plugin
 
 .release-plugin:
+  image: "python:3.10"
   stage: release
   before_script:
     - export VDK_PATCH_VERSION=${CI_PIPELINE_ID}
@@ -89,7 +90,7 @@
     - echo "Build and release vdk image of plugin $PLUGIN_NAME"
     - cd $PLUGIN_NAME/ || exit 1
     - sed -ri "s/__version__ = \"([[:digit:]]\.[[:digit:]]\.).*\"$/__version__ = \"\1${VDK_PATCH_VERSION}\"/g" setup.py
-    - apk add --no-cache git bash python3
+    - apk add --no-cache git bash python3 py3-pip
     - python3 -V
     - python3 -m pip install -U setuptools configparser
     - export VDK_PACKAGE=$(python3 setup.py --name)

projects/vdk-plugins/quickstart-vdk/.plugin-ci.yml

@@ -1,13 +1,6 @@
 # Copyright 2021-2023 VMware, Inc.
 # SPDX-License-Identifier: Apache-2.0
 
-image: "python:3.7"
-
-variables:
-  DOCKER_HOST: tcp://localhost:2375
-  DOCKER_DRIVER: overlay2
-  DOCKER_TLS_CERTDIR: ""
-
 # Add all quickstart-vdk dependencies locations which trigger the dependency release when changed.
 # In this way, quickstart-vdk will always be tested before one or more dependencies are changed, and
 # this is important since quickstart-vdk has unpinned dependencies and when they are upgraded,
@@ -78,6 +71,7 @@ quickstart-vdk-release-candidate-base-image:
   extends: .release-vdk-image
 
 quickstart-vdk-release-acceptance-test:
+  image: "python:3.10"
   stage: pre_release_test
   before_script:
     - export VDK_PATCH_VERSION=${CI_PIPELINE_ID}.dev${CI_PIPELINE_IID}