internal: move shim and init into app

This structure makes more sense, as both processes are part of an app's lifecycle.

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

internal/app/app.go

@@ -5,8 +5,8 @@ import (
 	"sync"
 
 	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/internal/app/shim"
 	"git.gensokyo.uk/security/fortify/internal/linux"
-	"git.gensokyo.uk/security/fortify/internal/priv/shim"
 )
 
 type App interface {