Update depguard rules to prevent importing test code outside tests

There is a lot of shared test code defined outside of _test.go
files scattered through out the code base. Dead code detection in
Go is not that great and cannot detect that these test helpers are
only consumed in tests. This results in testify code being included
in production binaries:

```bash
strings build/teleport | rg testify
github.com/stretchr/testify/assert.init
github.com/stretchr/testify/assert.uint32Type
go:link.pkghashbytes.github.com/stretchr/testify/assert
github.com/stretchr/testify/assert.int64Type
github.com/stretchr/testify/assert.uintptrType
go:link.pkghashbytes.github.com/stretchr/testify/require
github.com/stretchr/testify/assert.stringType
github.com/stretchr/testify/assert.float32Type
github.com/stretchr/testify/assert.bytesType
github.com/stretchr/testify/assert.intType
go:link.pkghashbytes.github.com/stretchr/testify/assert/yaml
github.com/stretchr/testify/assert.float64Type
github.com/stretchr/testify/assert..inittask
github.com/stretchr/testify/assert.int32Type
github.com/stretchr/testify/assert.uint16Type
github.com/stretchr/testify/assert.int8Type
github.com/stretchr/testify/assert.uint64Type
github.com/stretchr/testify/assert.uintType
github.com/stretchr/testify/assert.uint8Type
go:link.pkghash.github.com/stretchr/testify/assert/yaml
github.com/stretchr/testify/assert.int16Type
go:link.pkghash.github.com/stretchr/testify/require
go:link.pkghash.github.com/stretchr/testify/assert
github.com/stretchr/testify/assert.timeType
dep     github.com/stretchr/testify     v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
github.com/stretchr/testify/assert.init
github.com/stretchr/[email protected]/assert/assertion_compare.go
dep     github.com/stretchr/testify     v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
```

While this doesn't remediate anything, it should hopeful avoid any
future code from making it harder to separate test and production
code.

.golangci.yml

@@ -128,6 +128,64 @@ linters-settings:
             desc: 'use "log/slog" instead'
           - pkg: golang.org/x/exp/slog
             desc: 'use "log/slog" instead'
+            # Prevent importing any additional logging libraries.
+      testify:
+        files:
+          # Tests can import testify
+          - '!$test'
+          # Execptions
+          # Remove these once they are complaint.
+          - '!**/e/lib/auth/ssotestlib.go'
+          - '!**/e/lib/aws/identitycenter/test/**'
+          - '!**/e/lib/idp/saml/testenv/**'
+          - '!**/e/lib/operatortest/**'
+          - '!**/e/tests/**'
+          - '!**/lib/automaticupgrades/basichttp/servermock.go'
+          - '!**/lib/auth/helpers.go'
+          - '!**/lib/auth/keystore/testhelpers.go'
+          - '!**/lib/auth/test/**'
+          - '!**/lib/backend/test/**'
+          - '!**/lib/events/athena/test.go'
+          - '!**/lib/events/test/**'
+          - '!**/lib/kube/proxy/utils_testing.go'
+          - '!**/lib/services/suite/**'
+          - '!**/lib/srv/mock.go'
+          - '!**/lib/srv/db/redis/test.go'
+          - '!**/lib/teleterm/gatewaytest/**'
+          - '!**/lib/utils/testhelpers.go'
+          - '!**/lib/utils/testutils/**'
+          - '!**/integration/appaccess/fixtures.go'
+          - '!**/integration/appaccess/jwt.go'
+          - '!**/integration/appaccess/pack.go'
+          - '!**/integration/db/fixture.go'
+          - '!**/integration/hsm/helpers.go'
+          - '!**/integration/helpers/**'
+          - '!**/integration/proxy/proxy_helpers.go'
+          - '!**/integrations/access/email/testlib/**'
+          - '!**/integrations/access/datadog/testlib/**'
+          - '!**/integrations/access/discord/testlib/**'
+          - '!**/integrations/access/jira/testlib/**'
+          - '!**/integrations/access/mattermost/testlib/**'
+          - '!**/integrations/access/msteams/testlib/**'
+          - '!**/integrations/access/opsgenie/testlib/**'
+          - '!**/integrations/access/pagerduty/testlib/**'
+          - '!**/integrations/access/servicenow/testlib/**'
+          - '!**/integrations/access/slack/testlib/**'
+          - '!**/integrations/lib/testing/integration/accessrequestsuite.go'
+          - '!**/integrations/lib/testing/integration/app.go'
+          - '!**/integrations/lib/testing/integration/authhelper.go'
+          - '!**/integrations/lib/testing/integration/suite.go'
+          - '!**/integrations/operator/controllers/resources/testlib/**'
+          - '!**/tool/teleport/testenv/**'
+        deny:
+          - pkg: github.com/stretchr/testify
+            desc: 'testify should not be imported outside of test code'
+      integration:
+        files:
+          - '!**/integration/**'
+        deny:
+          - pkg: github.com/gravitational/teleport/integration$
+            desc: 'integration test could should not be imported outside of intergation tests'
       # Prevent importing internal packages in client tools or packages containing
       # common interfaces consumed by them that are known to bloat binaries or break builds
       # because they only support a single platform.