TUN-4063: Cleanup dependencies between packages.

- Move packages the provide generic functionality (such as config) from `cmd` subtree to top level.
- Remove all dependencies on `cmd` subtree from top level packages.
- Consolidate all code dealing with token generation and transfer to a single cohesive package.

origin/proxy.go

@@ -9,12 +9,12 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/cloudflare/cloudflared/buffer"
+	"github.com/pkg/errors"
+	"github.com/rs/zerolog"
+
 	"github.com/cloudflare/cloudflared/connection"
 	"github.com/cloudflare/cloudflared/ingress"
 	tunnelpogs "github.com/cloudflare/cloudflared/tunnelrpc/pogs"
-	"github.com/pkg/errors"
-	"github.com/rs/zerolog"
 )
 
 const (
@@ -26,7 +26,7 @@ type proxy struct {
 	warpRouting  *ingress.WarpRoutingService
 	tags         []tunnelpogs.Tag
 	log          *zerolog.Logger
-	bufferPool   *buffer.Pool
+	bufferPool   *bufferPool
 }
 
 func NewOriginProxy(
@@ -40,7 +40,7 @@ func NewOriginProxy(
 		warpRouting:  warpRouting,
 		tags:         tags,
 		log:          log,
-		bufferPool:   buffer.NewPool(512 * 1024),
+		bufferPool:   newBufferPool(512 * 1024),
 	}
 }