fix(cluster_select): gate Thread clusters on OPENTHREAD_ENABLED (CON-1993)

[cleishm]

Summary

• Add depends on OPENTHREAD_ENABLED to the three Thread-related cluster Kconfig entries (Thread Network Diagnostics, Thread Border Router Management, Thread Network Directory) so they are only enabled when OpenThread is present
• Update generate_cluster_select_files.py to emit the dependency for Thread clusters when regenerating

Problem

On WiFi-only devices (e.g. ESP32-S3), CONFIG_SUPPORT_THREAD_NETWORK_DIAGNOSTICS_CLUSTER and the other two Thread cluster configs default to y unconditionally. This causes the clusters to be created on the root node endpoint, but since CHIP_DEVICE_CONFIG_ENABLE_THREAD is disabled, attribute reads fail with CHIP_ERROR_NOT_IMPLEMENTED (error 0x2d). This produces noisy errors during Matter subscription:

E (7684) chip[DMG]: Fail to retrieve data, roll back and encode status on clusterId: 0x0000_0035, attributeId: 0x0000_0000 err = 2d

The errors are harmless (controllers handle the status responses), but they indicate unnecessary cluster registration and produce ~17 error lines on every subscription.

Fix

The generated Kconfig.in entries for the three Thread clusters now include depends on OPENTHREAD_ENABLED, so they can only be enabled when the OpenThread stack is actually available. On WiFi-only targets, the clusters won't be registered and controllers won't attempt to read their attributes.

Test plan

• Build and flash a WiFi-only device (e.g. ESP32-S3) — confirm Thread diagnostic clusters are not created and no 0x0035 DMG errors appear
• Build and flash a Thread-capable device (e.g. ESP32-H2/C6 with CONFIG_OPENTHREAD_ENABLED=y) — confirm Thread clusters are still created and functional