Provide ChatGLM support for "generate test"

Related Issue:

• https://jihulab.com/gitlab-cn/gitlab/-/issues/3101
• https://jihulab.com/gitlab-cn/gitlab/-/issues/3010

What does this MR do and why?

Integrate ChatGLM to support generate_test_file feature.

Take the test file generated by AI as an example, replace OpenAI with ChatGLM.

Screenshots or screen recordings

OpenAI	ChatGLM

How to set up and validate locally

Setup group:

project = Project.find(23)
namespace = project.root_ancestor

namespace.update!(experiment_features_enabled: true, third_party_ai_features_enabled: true)
namespace.gitlab_subscription.update!(plan_code: 'ultimate', trial: false, end_date: nil, seats: 100)

Setup ChatGLM Token:

export CHAT_GLM_API_KEY="<API-KEY>"

• Simulate a SaaS instance
• Feature.enable(:openai_experimentation)
• Feature.enable(:ai_related_settings, namespace)
• Feature.enable(:generate_test_file_flag, user)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.