chart: remove subnet finalizers before subnets are deleted

[zhangzujian]

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

What type of this PR

• Bug fixes

Which issue(s) this PR fixes:

#3169

WHAT

🤖 Generated by Copilot at 712199e

This pull request improves the GitHub Actions workflow, the OVS and OVN upgrade process, and the Kube-OVN chart uninstallation. It renames some jobs and containers, adds a cleanup step, a pre-delete hook, and a new make target. It affects the files .github/workflows/build-x86-image.yaml, charts/templates/upgrade-ovs-ovn.yaml, charts/templates/pre-delete-hook.yaml, and Makefile.

🤖 Generated by Copilot at 712199e

We unleash the hook of doom
To purge the finalizers from the subnets
We test the chart with helm and make
To ensure the Kube-OVN image is flawless

HOW

🤖 Generated by Copilot at 712199e

• Rename the chart installation test job to chart-test for consistency and clarity (link)
• Add a step to uninstall the Kube-OVN chart after testing it to clean up resources (link, link)
• Add a pre-delete hook to the Kube-OVN chart to remove finalizers from subnets before deleting the chart, to avoid subnets being stuck in terminating state (link)
• Rename the post-upgrade job and container to {{ .Chart.Name }}-post-upgrade-hook and ovs-ovn-upgrade respectively, to be more descriptive and avoid conflicts (link, link)