loader: pass loader environment to kernel as module
To simplify dealing with properties, we can just pack the loader environment as virtual module an pass it to kernel as name=value pairs. To identify the module, we set the name and type for module as:
so the kernel can recognize this module and use it. For property processing, the properties passed on kernel command line via -B, will always take precedence over values in environment. This way the operator can always override the values in environment.
To simplify the distinction, if the environment module is supported or not, we do implement it only via multiboot2 protocol.