Refactor/project structure (#3085)

* refactor project structure

* environment-based default registry

* fix tests

* update build container

* use docker platform for iso build emulation

* simplify compat

* Fix docker platform spec in run-compat.sh

* handle riscv compat

* fix bug with dep error exists attr

* undo removal of sorting

* use qemu for iso stage

---------

Co-authored-by: Mariusz Kogen <k0gen@pm.me>
Co-authored-by: Matt Hill <mattnine@protonmail.com>

build/image-recipe/README.md

@@ -0,0 +1,19 @@
+# StartOS Image Recipes
+
+Code and `debos` recipes that are used to create the StartOS live and installer
+images.
+
+If you want to build a local image in the exact same environment used to build
+official StartOS images, you can use the `run-local-build.sh` helper script:
+
+```bash
+# Prerequisites
+sudo apt-get install -y debspawn binfmt-support
+sudo mkdir -p /etc/debspawn/ && echo "AllowUnsafePermissions=true" | sudo tee /etc/debspawn/global.toml
+
+# Build image
+./run-local-build.sh
+```
+
+In order for the build to work properly, you will need debspawn >= 0.5.1, the
+build may fail with prior versions.