refactor: move tunnel pkg down one level (#358)

* refactor: move tunnel pkg down one level

While there, reduce unnecessary dependency on external packages.

* file I forgot to commit

internal/engine/tunnel/psiphon.go

@@ -1,76 +0,0 @@
-package tunnel
-
-import (
-	"context"
-	"fmt"
-	"net"
-	"net/url"
-	"path/filepath"
-	"time"
-
-	"github.com/ooni/psiphon/oopsi/github.com/Psiphon-Labs/psiphon-tunnel-core/ClientLibrary/clientlib"
-)
-
-// psiphonTunnel is a psiphon tunnel
-type psiphonTunnel struct {
-	// bootstrapTime is the bootstrapTime of the bootstrap
-	bootstrapTime time.Duration
-
-	// tunnel is the underlying psiphon tunnel
-	tunnel *clientlib.PsiphonTunnel
-}
-
-// psiphonMakeWorkingDir creates the working directory
-func psiphonMakeWorkingDir(config *Config) (string, error) {
-	workdir := filepath.Join(config.TunnelDir, config.Name)
-	if err := config.mkdirAll(workdir, 0700); err != nil {
-		return "", err
-	}
-	return workdir, nil
-}
-
-// psiphonStart starts the psiphon tunnel.
-func psiphonStart(ctx context.Context, config *Config) (Tunnel, error) {
-	select {
-	case <-ctx.Done():
-		return nil, ctx.Err() // simplifies unit testing this code
-	default:
-	}
-	if config.TunnelDir == "" {
-		return nil, ErrEmptyTunnelDir
-	}
-	configJSON, err := config.Session.FetchPsiphonConfig(ctx)
-	if err != nil {
-		return nil, err
-	}
-	workdir, err := psiphonMakeWorkingDir(config)
-	if err != nil {
-		return nil, err
-	}
-	start := time.Now()
-	tunnel, err := config.startPsiphon(ctx, configJSON, workdir)
-	if err != nil {
-		return nil, err
-	}
-	stop := time.Now()
-	return &psiphonTunnel{tunnel: tunnel, bootstrapTime: stop.Sub(start)}, nil
-}
-
-// Stop is an idempotent method that shuts down the tunnel
-func (t *psiphonTunnel) Stop() {
-	t.tunnel.Stop()
-}
-
-// SOCKS5ProxyURL returns the SOCKS5 proxy URL.
-func (t *psiphonTunnel) SOCKS5ProxyURL() *url.URL {
-	return &url.URL{
-		Scheme: "socks5",
-		Host: net.JoinHostPort(
-			"127.0.0.1", fmt.Sprintf("%d", t.tunnel.SOCKSProxyPort)),
-	}
-}
-
-// BootstrapTime returns the bootstrap time
-func (t *psiphonTunnel) BootstrapTime() time.Duration {
-	return t.bootstrapTime
-}