feat(build): introduce build configuration for channel inclusion

[kaviraj-j]

• Add build.yaml.example for configuring which channels to compile into the binary.
• Implement genbuild script to generate channel imports based on build.yaml.
• Update Makefile to run genbuild automatically during the build process.
• Create documentation in BUILD_CONFIG.md to guide users on configuring and using the build system.
• Move channel imports to channels_imports.go, generated by genbuild, to reduce binary size.

📝 Description

• This PR adds a configurable build system for channels.
• Channels included in the final binary are determined through a build configuration file, allowing only the required channels to be compiled.
• If no configuration is provided, all available channels are included by default.

🗣️ Type of Change

• 🐞 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 📖 Documentation update
• ⚡ Code refactoring (no functional changes, no api changes)

🤖 AI Code Generation

• 🤖 Fully AI-generated (100% AI, 0% Human)
• 🛠️ Mostly AI-generated (AI draft, Human verified/modified)
• 👨‍💻 Mostly Human-written (Human lead, AI assisted or none)

🔗 Related Issue

Closes #923

📚 Technical Context

• Reasoning:
  Previously, all channel implementations were always compiled into the binary, increasing binary size and including unused dependencies. This change introduces a generation step that reads a build configuration file and dynamically creates the required channel imports during the build process. The generated imports file ensures that only selected channels are compiled, resulting in a more modular build and reduced binary size while keeping the build workflow automated.

🧪 Test Environment

• Hardware: PC
• OS: macOS 15.6.1 24G90 arm64

📸 Evidence

Details

Size difference between including all channel implementation in the build vs only including Telegram

☑️ Checklist

• My code/docs follow the style of this project.
• I have performed a self-review of my own changes.
• I have updated the documentation accordingly.

[xiaket]

I have a concern over this approach.

We will need a discussion on whether we want this feature before we can take this in, and if we want it, what is the best way to implement it. For example, what are the things we would like to customise, and how to best group them.

The current approach of having a go cmd as a script feels pre-mature for me.

[CLAassistant]

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[sipeed-bot]

@kaviraj-j Hi! This PR has had no activity for over 2 weeks, so I'm closing it for now to keep things organized. Feel free to reopen anytime if you'd like to continue.