doc: release-notes-4.0: Add notes for Wi-Fi

* Wi-Fi

  * Added ESP32-C2 Wi-Fi support.

  * Added ESP32 driver APSTA support.

  * Add Wi-Fi Easy Connect (DPP) support.

  * Add support for Wi-Fi credentials library.

  * Add enterprise support for station.

  * Add Wi-Fi snippet support for networking samples.

  * Add build testing for various Wi-Fi config combinations.

  * Add regulatory domain support to Wi-Fi shell.

  * Add WPS support to Wi-Fi shell.

  * Add 802.11r connect command usage in Wi-Fi shell.

  * Add current PHY rate to hostap status message.

  * Allow user to reset Wi-Fi statistics in Wi-Fi shell.

  * Display RTS threshold in Wi-Fi shell.

  * Fix SSID array length size in scanning results.

  * Fix the "wifi ap config" command using the STA interface instead of SAP interface.

  * Fix memory leak in hostap when doing a disconnect.

  * Fix setting of frequency band both in AP and STA mode in Wi-Fi shell.

  * Fix correct channel scan range in Wi-Fi 6GHz.

  * Fix scan results printing in Wi-Fi shell.

  * Increase main and shell stack sizes for Wi-Fi shell sample.

  * Increase the maximum count of connected STA to 8 in Wi-Fi shell.

  * Relocate AP and STA Wi-Fi sample to samples/net/wifi directory.

  * Run Wi-Fi tests together with network tests.

  * Updated ESP32 Wi-Fi driver to reflect actual negotiated PHY mode.

  * Add ESP32-C2 Wi-Fi support.

  * Add ESP32 driver APSTA support.

  * Add NXP RW612 driver support.

Networking

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