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/spark/setup_test.go

@@ -14,7 +14,7 @@ import (
 	"github.com/aws/aws-sdk-go-v2/aws"
 	"github.com/aws/aws-sdk-go-v2/credentials"
 	"github.com/aws/aws-sdk-go-v2/service/s3"
-	"github.com/seaweedfs/seaweedfs/test/s3tables/testutil"
+	"github.com/seaweedfs/seaweedfs/test/testutil"
 	"github.com/testcontainers/testcontainers-go"
 )
 
@@ -94,9 +94,10 @@ func (env *TestEnvironment) StartSeaweedFS(t *testing.T) {
 		t.Fatalf("failed to create temp directory: %v", err)
 	}
 
-	env.masterPort = testutil.MustFreeMiniPort(t, "Master")
-	env.filerPort = testutil.MustFreeMiniPort(t, "Filer")
-	env.s3Port = testutil.MustFreeMiniPort(t, "S3")
+	ports := testutil.MustFreeMiniPorts(t, []string{"Master", "Filer", "S3"})
+	env.masterPort = ports[0]
+	env.filerPort = ports[1]
+	env.s3Port = ports[2]
 
 	bindIP := testutil.FindBindIP()
 	iamConfigPath, err := testutil.WriteIAMConfig(env.seaweedfsDataDir, env.accessKey, env.secretKey)