test: add test of getChartSpecWithContext when chartType is treemap

[yatbfm]

[中文版模板 / Chinese template]

🤔 This is a ...

• [ ] New feature
• [ ] Bug fix
• [ ] TypeScript definition update
• [ ] Bundle size optimization
• [ ] Performance optimization
• [ ] Enhancement feature
• [ ] Refactoring
• [ ] Update dependency
• [ ] Code style optimization
• [x] Test Case
• [ ] Branch merge
• [ ] Release
• [ ] Site / documentation update
• [ ] Demo update
• [ ] Workflow
• [ ] Other (about what?)

🔗 Related issue link

releated #232

🔗 Related PR link

🐞 Bugserver case id

💡 Background and solution

📝 Changelog

Add treemap related test cases. Test cell.color for single and multiple scenarios.

Language	Changelog
🇺🇸 English	Add treemap related test cases
🇨🇳 Chinese	添加树图相关测试用例

☑️ Self-Check before Merge

⚠️ Please check all items below before requesting a reviewing. ⚠️

• [x] Doc is updated/provided or not needed
• [x] Demo is updated/provided or not needed
• [x] TypeScript definition is updated/provided or not needed
• [x] Changelog is provided or not needed

---

🚀 Summary

copilot:summary

🔍 Walkthrough

copilot:walkthrough