refactor(test): use gomock for Delivery with mocks folder structure

## Summary

Replace manual mockDelivery with gomock-generated mock in a dedicated mocks package.

## What Changed

**Delivery Mock:**
- Generate gomock in extension/queue/mocks/ package
- Add go:generate directive to delivery.go
- Create extension/queue/mocks/BUILD.bazel

**Request Controller Tests:**
- Update request_test.go to use mocks.NewMockDelivery
- Add Message() and Attempt() expectations (controller calls these for logging)
- Remove 45 lines of manual mockDelivery struct
- Add mocks package dependency to BUILD.bazel

## Why Gomock in Mocks Folder?

1. Already used in codebase (extension/queue/sql)
2. Organized structure - mocks in dedicated package
3. Eliminates duplicate manual mocks
4. Better type safety and compile-time verification
5. Easier to maintain with go:generate directive

## Files Changed

- extension/queue/delivery.go (go:generate directive)
- extension/queue/mocks/delivery.go (new - generated mock)
- extension/queue/mocks/BUILD.bazel (new - bazel build)
- orchestrator/controller/request/request_test.go (use gomock)
- orchestrator/controller/request/BUILD.bazel (add mocks dep)
- orchestrator/controller/BUILD.bazel (gazelle formatting)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: behinddwalls

extension/queue/delivery.go

@@ -1,5 +1,7 @@
 package queue
 
+//go:generate mockgen -source=delivery.go -destination=mocks/delivery.go -package=mocks
+
 import (
 	"context"
 

extension/queue/mocks/BUILD.bazel

@@ -0,0 +1,12 @@
+load("@rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "mocks",
+    srcs = ["delivery.go"],
+    importpath = "github.com/uber/submitqueue/extension/queue/mocks",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//entity/queue",
+        "@org_uber_go_mock//gomock",
+    ],
+)

extension/queue/mocks/delivery.go

@@ -2,9 +2,7 @@ load("@rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "controller",
-    srcs = [
-        "ping.go",
-    ],
+    srcs = ["ping.go"],
     importpath = "github.com/uber/submitqueue/orchestrator/controller",
     visibility = ["//visibility:public"],
     deps = [
@@ -16,16 +14,13 @@ go_library(
 
 go_test(
     name = "controller_test",
-    srcs = [
-        "ping_test.go",
-    ],
+    srcs = ["ping_test.go"],
     embed = [":controller"],
     deps = [
         "//orchestrator/protopb",
         "@com_github_stretchr_testify//assert",
         "@com_github_stretchr_testify//require",
         "@com_github_uber_go_tally_v4//:tally",
         "@org_uber_go_zap//:zap",
-        "@org_uber_go_zap//zaptest",
     ],
 )

orchestrator/controller/BUILD.bazel

@@ -2,9 +2,7 @@ load("@rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "request",
-    srcs = [
-        "request.go",
-    ],
+    srcs = ["request.go"],
     importpath = "github.com/uber/submitqueue/orchestrator/controller/request",
     visibility = ["//visibility:public"],
     deps = [
@@ -18,17 +16,17 @@ go_library(
 
 go_test(
     name = "request_test",
-    srcs = [
-        "request_test.go",
-    ],
+    srcs = ["request_test.go"],
     embed = [":request"],
     deps = [
         "//entity",
         "//entity/queue",
         "//extension/queue",
+        "//extension/queue/mocks",
         "@com_github_stretchr_testify//assert",
         "@com_github_stretchr_testify//require",
         "@com_github_uber_go_tally_v4//:tally",
+        "@org_uber_go_mock//gomock",
         "@org_uber_go_zap//zaptest",
     ],
 )