metropolis/node: move misplaced packages out of core

abloader, bios_bootcode and minit don't run as part of the core process,
so it doesn't make sense to have them in //metropolis/node/core.
This changes moves these three to //metropolis/node.

Change-Id: I908efb311a138f07a9f1de8e3c23437ff00131ee
Reviewed-on: https://review.monogon.dev/c/monogon/+/4196
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
Tested-by: Jenkins CI
diff --git a/cloud/agent/install.go b/cloud/agent/install.go
index a59664e..6deffab 100644
--- a/cloud/agent/install.go
+++ b/cloud/agent/install.go
@@ -27,7 +27,7 @@
 	"source.monogon.dev/osbase/supervisor"
 )
 
-//go:embed metropolis/node/core/abloader/abloader_bin.efi
+//go:embed metropolis/node/abloader/abloader_bin.efi
 var abloader []byte
 
 // install dispatches OSInstallationRequests to the appropriate installer