test(queue/sql): add comprehensive e2e integration tests

Why?
The SQL queue implementation needs thorough integration testing against
a real MySQL database to validate end-to-end functionality including:
- Message publishing and consumption workflows
- Partition management and isolation
- Visibility timeout and retry mechanisms
- DLQ (Dead Letter Queue) handling
- Concurrency and crash recovery scenarios
- Consumer group coordination and load balancing

Without these tests, we cannot verify that the queue behaves correctly
in production-like scenarios with a real database.

What?
- Add 15 comprehensive integration tests using testcontainers-go:
  * Basic operations: publish/subscribe, metadata preservation
  * Partition management: multiple partitions, isolation
  * Reliability: visibility timeout, retry, nack with delay
  * Correctness: idempotent publish, message ordering
  * Concurrency: concurrent publishers, concurrent subscribers
  * Crash recovery: lease expiration and message recovery
  * Consumer groups: multiple groups, multiple workers, load balancing
  * DLQ: max retries, DLQ metadata, failure tracking
  * Edge cases: late subscriber, empty topic, graceful shutdown

- Add integration_tests/queue/README.md with:
  * Test coverage documentation
  * Prerequisites (Docker)
  * Running instructions (Bazel, go test, verbose output)
  * Test descriptions and what each validates

- Refactor integration_tests/testutil for reusability:
  * Extract MySQL container utilities to testutil/mysql.go
  * Share MySQL setup across integration test suites
  * Add schema application helpers

- Test infrastructure improvements:
  * Use testify/suite for setup/teardown lifecycle
  * Tag tests with "integration" for selective execution
  * Support for verbose test output (--test_arg=-test.v)
  * Proper container cleanup in all scenarios

All 15 tests passing in ~2 minutes runtime.

Co-Authored-By: Preetam Dwivedi <preetam@uber.com>

Author: behinddwalls

integration_tests/BUILD.bazel

@@ -5,7 +5,6 @@ load("@rules_go//go:def.bzl", "go_test")
 go_test(
     name = "integration_test",
     srcs = [
-        "mysql.go",
         "servers.go",
         "suite_test.go",
     ],
@@ -18,6 +17,7 @@ go_test(
     ],
     tags = ["integration"],
     deps = [
+        "//integration_tests/testutil",
         "//gateway/protopb",
         "//orchestrator/protopb",
         "//speculator/protopb",

integration_tests/mysql.go

@@ -0,0 +1,25 @@
+load("@rules_go//go:def.bzl", "go_test")
+
+go_test(
+    name = "queue_test",
+    srcs = ["queue_test.go"],
+    data = [
+        "//extensions/queue/sql/schema",
+    ],
+    tags = ["integration"],
+    deps = [
+        "//entities/queue",
+        "//extensions/queue",
+        "//extensions/queue/sql",
+        "//integration_tests/testutil",
+        "@com_github_go_sql_driver_mysql//:mysql",
+        "@com_github_stretchr_testify//assert",
+        "@com_github_stretchr_testify//require",
+        "@com_github_stretchr_testify//suite",
+        "@com_github_testcontainers_testcontainers_go//:testcontainers-go",
+        "@com_github_testcontainers_testcontainers_go//network",
+        "@com_github_testcontainers_testcontainers_go_modules_mysql//:mysql",
+        "@com_github_uber_go_tally_v4//:tally",
+        "@org_uber_go_zap//zaptest",
+    ],
+)