fix: major build system improvements and container output issues

- Fix container output visibility with proper TTY handling and debug mode
- Fix build order: kernel modules built before initramfs creation
- Implement two-stage kernel build to resolve chicken-and-egg dependency
- Fix sed command issues in kernel configuration with direct execution
- Add diffutils package to container for proper kernel build support
- Enhance NIC module/firmware correlation with intelligent selection
- Fix module staging logic: all NICs loaded in stage1 before network up
- Add smart firmware installation based on module requirements
- Create comprehensive function documentation (scripts/functionlist.md)
- Add debug container script for troubleshooting

Major fixes:
* Container builds now show real-time output
* Kernel builds work with proper GNU diff support
* Module/firmware selection optimized for common hardware
* Build process handles dependencies correctly
* Documentation provides complete function reference

config/sources.conf

@@ -4,7 +4,7 @@
 # Git repositories to clone and build
 git zinit https://github.com/threefoldtech/zinit master build_zinit
 git mycelium https://github.com/threefoldtech/mycelium v0.6.1 build_mycelium
-git rfs https://github.com/threefoldtech/rfs development build_rfs
 
 # Pre-built releases to download
+release rfs https://github.com/threefoldtech/rfs/releases/download/v2.0.6/rfs v2.0.6 install_rfs
 release corex https://github.com/threefoldtech/corex/releases/download/2.1.4/corex-2.1.4-amd64-linux-static 2.1.4 install_corex rename=corex