internal/app: rename init to init0

This makes way for the new container init.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/init0/payload.go

@@ -0,0 +1,13 @@
+package init0
+
+const Env = "FORTIFY_INIT"
+
+type Payload struct {
+	// target full exec path
+	Argv0 string
+	// child full argv
+	Argv []string
+
+	// verbosity pass through
+	Verbose bool
+}