Go v4

[cb-srinaths]

🚀 Pull Request Template

📘 Description

• Added a new GO_V4 SDK generated at https://github.com/chargebee/chargebee-go/tree/v4
• Split out the existing Go completely, so we now have GO_V3 and GO_V4 which can be generated and maintained in parallel

🧩 Related Issues / Tickets

Closes #IssueNumber

📂 Type of Change

• ✨ Feature
• 🐛 Bug Fix
• 📝 Documentation
• 🧪 Test Improvement
• 🔧 Refactor / Code Cleanup
• ⚙️ Build / Tooling

🧪 How to Test

# Go V4
./scripts/sdk-gen.sh generate go-v4

# Go V3
./scripts/sdk-gen.sh generate go

[snyk-io]

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✅	Licenses	0	0	0	0	0 issues

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[hivel-marco]

PR has too many lines changed - Skipping review. Please keep lines changed under 2000 for high quality reviews