Upgrade repository to Go 1.18.

Steps taken:

1. Ran `bazel build //infra/bots/...` and had the following errors:

    compilepkg: missing strict dependencies:
     /private/var/tmp/.../sandbox/darwin-sandbox/781/execroot/skia/infra/bots/task_drivers/
    codesize/codesize_test.go: import of "github.com/stretchr/testify/mock"
     /private/var/tmp/.../sandbox/darwin-sandbox/781/execroot/skia/infra/bots/task_drivers/
    codesize/codesize_test.go: import of "go.skia.org/infra/go/util"

2. Added missing dependencies to infra/bots/task_drivers/codesize/BUILD.bazel
   which is included in this commit.

3. Ran `bazel build //infra/bots/...` - success.

4. Ran `go mod tidy` which resulted in no changes.

5. Ran `make -C bazel gazelle_update_repo` which resulted in no changes.

6. Ran `bazel build modules/canvaskit/go/...` - success.

Bug: skia:13605
Change-Id: Id8aa9a7d26f8849a7e602445c2b84c2586f589e2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/564923
Commit-Queue: Chris Mumford <cmumford@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
diff --git a/WORKSPACE.bazel b/WORKSPACE.bazel
index 6b4c4bb..f4a8ac8 100644
--- a/WORKSPACE.bazel
+++ b/WORKSPACE.bazel
@@ -117,7 +117,7 @@
 
 go_rules_dependencies()
 
-go_register_toolchains(version = "1.17.2")
+go_register_toolchains(version = "1.18")
 
 gazelle_dependencies(go_repository_default_config = "//:WORKSPACE.bazel")
 
diff --git a/infra/bots/task_drivers/codesize/BUILD.bazel b/infra/bots/task_drivers/codesize/BUILD.bazel
index 92d40a8..e504d48 100644
--- a/infra/bots/task_drivers/codesize/BUILD.bazel
+++ b/infra/bots/task_drivers/codesize/BUILD.bazel
@@ -40,6 +40,7 @@
     embed = [":codesize_lib"],
     deps = [
         "@com_github_stretchr_testify//assert",
+        "@com_github_stretchr_testify//mock",
         "@com_github_stretchr_testify//require",
         "@org_skia_go_infra//go/exec",
         "@org_skia_go_infra//go/gcs",
@@ -53,6 +54,7 @@
         "@org_skia_go_infra//go/mockhttpclient",
         "@org_skia_go_infra//go/now",
         "@org_skia_go_infra//go/testutils",
+        "@org_skia_go_infra//go/util",
         "@org_skia_go_infra//task_driver/go/td",
         "@org_skia_go_infra//task_scheduler/go/types",
     ],