ci: use ddk for faster ci, manual gki image build

[Ylarod]

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[Copilot]

Pull Request Overview

This PR introduces DDK (Development Driver Kit) integration for faster CI builds, restructures the build system to support both in-tree and out-of-tree builds, and simplifies the kernel build workflows. The changes focus on using pre-built container images with DDK for module builds while maintaining manual GKI image building through workflow dispatch.

• Integrates DDK containers for faster KernelSU module builds replacing the previous GKI kernel build approach
• Restructures Makefile to handle both in-tree and out-of-tree git repository detection and build scenarios
• Adds comprehensive VS Code development environment configuration with clangd integration

Reviewed Changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
kernel/Makefile	Enhanced git detection logic and added standalone build targets
kernel/.vscode/*	Complete VS Code workspace configuration for kernel development
.github/workflows/ddk-lkm.yml	New DDK-based LKM build workflow using containers
.github/workflows/build-lkm.yml	Simplified LKM build using DDK workflow
.github/workflows/build-kernel-*.yml	Disabled automatic triggers, added debug input support
.github/workflows/build-gki-image.yml	New manual GKI image build workflow
.github/workflows/build-debug-kernel.yml	Removed redundant debug build workflow

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