Fix flaky s3tables tests: allocate all ports atomically

The test port allocation had a TOCTOU race where GetFreePort() would
open a listener, grab the port number, then immediately close it.
When called repeatedly, the OS could recycle a just-released port,
causing two services (e.g. Filer and S3) to be assigned the same port.

Replace per-call GetFreePort() with batch AllocatePorts() that holds
all listeners open until every port is obtained, matching the pattern
already used in test/volume_server/framework/cluster.go.

test/s3tables/lakekeeper/lakekeeper_test.go

@@ -115,10 +115,13 @@ func NewTestEnvironment(t *testing.T) *TestEnvironment {
 
 	bindIP := testutil.FindBindIP()
 
-	masterPort, masterGrpcPort := testutil.MustFreePortPair(t, "Master")
-	volumePort, volumeGrpcPort := testutil.MustFreePortPair(t, "Volume")
-	filerPort, filerGrpcPort := testutil.MustFreePortPair(t, "Filer")
-	s3Port, s3GrpcPort := testutil.MustFreePortPair(t, "S3")
+	// Allocate all ports in a single batch to prevent the OS from recycling
+	// a released port, which can cause two services to get the same port.
+	ports := testutil.MustAllocatePorts(t, 8)
+	masterPort, masterGrpcPort := ports[0], ports[1]
+	volumePort, volumeGrpcPort := ports[2], ports[3]
+	filerPort, filerGrpcPort := ports[4], ports[5]
+	s3Port, s3GrpcPort := ports[6], ports[7]
 
 	return &TestEnvironment{
 		seaweedDir:     seaweedDir,