OVN IC: support ECMP mode

[zhangzujian]

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

What type of this PR

• Features

Which issue(s) this PR fixes:

Fixes #(issue-number)

WHAT

🤖 Generated by Copilot at f7de274

This pull request enhances the interconnection feature for kind clusters, which allows connecting multiple OVN-based Kubernetes clusters. It updates the Makefile to support this feature, improves the interconnection controller logic in pkg/controller/ovn-ic.go, and modifies the CreateICLogicalRouterPort function in pkg/ovs/ovn-nbctl-legacy.go to handle multiple transit switches per cluster.

🤖 Generated by Copilot at f7de274

Sing, O Muse, of the mighty deeds of the OVN developers,
Who, with skill and wisdom, enhanced the interconnection feature,
And made it possible for many clusters to join in harmony,
Through the transit switches, ts, that span the azure sea.

HOW

🤖 Generated by Copilot at f7de274

• Add support for multiple transit switches per cluster for the interconnection feature (link, link, link, link, link)
• Create transit switches in the interconnection database directly from the controller, instead of relying on the interconnection agent (link, link)
• Remove the taint from the control plane nodes in the kind clusters, to allow running pods on them for the interconnection feature (link)
• Remove unused and unnecessary code from the interconnection controller logic (link, link, link)
• Optimize and simplify the logic for syncing the learned routes to the logical router policies in the OVN database (link, link)
• Add SSL communication support for the interconnection database (link)
• Add new imports for the set data structure and the OVS and OVN utilities and constants (link, link)