perf: Add workflow template informer to server

[jakkubu]

Motivation

Improve performance of creating workflows with complex templateRef structure.

During template validation k8s API is called for each templateRef. For complex workflows with many refs it creates huge overhead. Let's cache such templates

Connected to issue https://github.com/argoproj/argo-workflows/issues/7418

This is a follow up PR #13633

Modifications

Added informer to the server and use it in workflow validation

Verification

I run the tests similar to the ones in 1st PR. The results are awesome - benchmarking results and details in separate comment