[improve][build] Build docker image only once when pushing

[nodece]

Motivation

When pushing images to Docker Hub, the docker-maven-plugin currently builds the image twice: once during the build goal and again during the push goal. This results in redundant work and unnecessary build time.

This change makes the Docker goal configurable so that the image is built only once when pushing.

Modifications

• Replaced the hardcoded Docker goals (build and push) in the default execution of the Docker Maven plugin with the ${docker.goal} property in both docker/pulsar/pom.xml and docker/pulsar-all/pom.xml, allowing the active goal to be configured.
• Set the default value of the docker.goal property to build in the root pom.xml, preserving the existing behavior for normal builds.
• Added the docker.goal=push property to the docker-push Maven profile in both docker/pulsar/pom.xml and docker/pulsar-all/pom.xml, so activating this profile pushes the image without triggering an extra build.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[lhotari]

LGTM

[lhotari]

/pulsarbot rerun-failure-checks