test: consolidate port allocation into shared test/testutil package (#8982)

* test: consolidate port allocation into shared test/testutil package

Move duplicated port allocation logic from 15+ test files into a single
shared package at test/testutil/. This fixes a port collision bug where
independently allocated ports could overlap via the gRPC offset
(port+10000), causing weed mini to reject the configuration.

The shared package provides:
- AllocatePorts: atomic allocation of N unique ports
- AllocateMiniPorts/MustFreeMiniPorts: gRPC-offset-aware allocation
  that prevents port A+10000 == port B collisions
- WaitForPort, WaitForService, FindBindIP, WriteIAMConfig, HasDocker

* test: address review feedback and fix FUSE build

- Revert fuse_integration change: it has its own go.mod and cannot
  import the shared testutil package
- AllocateMiniPorts: hold all listeners open until the entire batch is
  allocated, preventing race conditions where other processes steal ports
- HasDocker: add 5s context timeout to avoid hanging on stalled Docker
- WaitForService: only treat 2xx HTTP status codes as ready

* test: use global rand in AllocateMiniPorts for better seeding

Go 1.20+ auto-seeds the global rand generator. Using it avoids
identical sequences when multiple tests call at the same nanosecond.

* test: revert WaitForService status code check

S3 endpoints return non-2xx (e.g. 403) on bare GET requests, so
requiring 2xx caused the S3 integration test to time out. Any HTTP
response is sufficient proof that the service is running.

* test: fix gofmt formatting in s3tables test files

test/s3/distributed_lock/distributed_lock_cluster_test.go

@@ -20,6 +20,7 @@ import (
 	"github.com/aws/aws-sdk-go-v2/config"
 	"github.com/aws/aws-sdk-go-v2/credentials"
 	"github.com/aws/aws-sdk-go-v2/service/s3"
+	"github.com/seaweedfs/seaweedfs/test/testutil"
 	"github.com/seaweedfs/seaweedfs/test/volume_server/framework"
 	"github.com/seaweedfs/seaweedfs/weed/cluster/lock_manager"
 	"github.com/seaweedfs/seaweedfs/weed/pb"
@@ -115,7 +116,7 @@ func startDistributedLockCluster(t *testing.T) *distributedLockCluster {
 		require.NoError(t, os.MkdirAll(dir, 0o755), "create %s", dir)
 	}
 
-	ports, err := allocatePorts(12)
+	ports, err := testutil.AllocatePorts(12)
 	require.NoError(t, err, "allocate ports")
 	cluster.masterPort = ports[0]
 	cluster.masterGrpcPort = ports[1]
@@ -591,25 +592,6 @@ func (c *distributedLockCluster) tailLog(name string) string {
 	return strings.Join(lines, "\n")
 }
 
-func allocatePorts(count int) ([]int, error) {
-	listeners := make([]net.Listener, 0, count)
-	ports := make([]int, 0, count)
-	for i := 0; i < count; i++ {
-		l, err := net.Listen("tcp", "127.0.0.1:0")
-		if err != nil {
-			for _, openListener := range listeners {
-				_ = openListener.Close()
-			}
-			return nil, err
-		}
-		listeners = append(listeners, l)
-		ports = append(ports, l.Addr().(*net.TCPAddr).Port)
-	}
-	for _, l := range listeners {
-		_ = l.Close()
-	}
-	return ports, nil
-}
 
 func stopProcess(cmd *exec.Cmd) {
 	if cmd == nil || cmd.Process == nil {