some fixes in e2e

[zhangzujian]

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

What type of this PR

• Tests

Which issue(s) this PR fixes:

1. reduce possiblilty of the same name suffix;
2. fix e2e logging.

WHAT

🤖 Generated by Copilot at 8cc27de

The pull request improves the reliability, readability, and quality of the e2e test cases for kube-ovn by using random ports and names, enhancing log messages, and fixing minor bugs and code smells in the test packages. The changes affect the files service.go, subnet.go, underlay.go, e2e_test.go, and util.go.

🤖 Generated by Copilot at 8cc27de

Sing, O Muse, of the valiant pull request
That enhanced the test code of the framework
With random suffixes and ports, and log messages
That shone like the bright stars in the night sky.

HOW

🤖 Generated by Copilot at 8cc27de

• Increase the length of the random suffix for resource names to avoid conflicts (link)
• Use a random port between 8000 and 8999 for service tests to avoid port conflicts (link)
• Improve the log messages for creating and deleting provider networks in various packages (link, link, link, link, link, link, link, link)
• Fix the bug of checking the IPv6 cluster IP in the ipvsadm output by using field-based matching instead of string contains (link)
• Remove the redundant and unused assignment of the podName variable in the subnet package (link)
• Change the DstIPs field in the NatOutGoingPolicyMatch struct to use a non-reserved IP range (link)
• Simplify and clarify the code for generating the asName variable in the underlay package by using strings.ReplaceAll and a constant format string (link)