ci: fix dpdk jobs

[zhangzujian]

Pull Request

• Make sure you have followed Kube-OVN Code Style.

What type of this PR

Examples of user facing changes:

• Features
• Bug fixes
• Docs
• Tests

Which issue(s) this PR fixes

Fixes #(issue-number)

WHAT

🤖 Generated by Copilot at c5a5663

This pull request adds support for building and using a dpdk image for the kube-ovn project. It modifies the .github/workflows/build-x86-image.yaml file to optimize the workflow for pull request events, and it adds new targets to the Makefile for the dpdk image.

🤖 Generated by Copilot at c5a5663

Sing, O Muse, of the skillful pull request
That optimized the workflow of the build
And spared the steps of dpdk base images
When triggered by a pull request event.

HOW

🤖 Generated by Copilot at c5a5663

• Add a new target to build the dpdk image using the dpdk base image as a base image, and tag it with the release tag and the dpdk suffix (link, link)
• Add a new step to the workflow to build and upload the dpdk image to artifact using the Makefile target (link, link)
• Add a new target to save the dpdk image into a tar file (link)
• Remove the redundant tag for the dpdk base image (link)
• Skip downloading, loading, and uploading dpdk base images when the workflow is triggered by a pull request, since they are not needed for testing or reviewing the pull request (link, link, link)