all: remove deprecated packages

Closes #24.

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

system/deprecated.go

@@ -1,50 +0,0 @@
-// Package system exposes the internal/system package.
-//
-// Deprecated: This package will be removed in 0.4.
-package system
-
-import (
-	"context"
-	_ "unsafe" // for go:linkname
-
-	"hakurei.app/hst"
-	"hakurei.app/internal/system"
-	"hakurei.app/message"
-)
-
-// ErrDBusConfig is returned when a required hst.BusConfig argument is nil.
-//
-//go:linkname ErrDBusConfig hakurei.app/internal/system.ErrDBusConfig
-var ErrDBusConfig error
-
-// OpError is returned by [I.Commit] and [I.Revert].
-type OpError = system.OpError
-
-const (
-	// User type is reverted at final instance exit.
-	User = system.User
-	// Process type is unconditionally reverted on exit.
-	Process = system.Process
-
-	CM = system.CM
-)
-
-// Criteria specifies types of Op to revert.
-type Criteria = system.Criteria
-
-// Op is a reversible system operation.
-type Op = system.Op
-
-// TypeString extends [Enablement.String] to support [User] and [Process].
-//
-//go:linkname TypeString hakurei.app/internal/system.TypeString
-func TypeString(e hst.Enablement) string
-
-// New returns the address of a new [I] targeting uid.
-//
-//go:linkname New hakurei.app/internal/system.New
-func New(ctx context.Context, msg message.Msg, uid int) (sys *I)
-
-// An I provides deferred operating system interaction. [I] must not be copied.
-// Methods of [I] must not be used concurrently.
-type I = system.I