NFC / RFID Detector does not put NFC in low power mode on exit

[peterfab9845]

The NFC/RFID Detector app does not use furi_hal_nfc_low_power_mode_stop()/furi_hal_nfc_low_power_mode_start(), so when it is exited, the NFC hardware is left active.
This results in an extra idle power drain of a few mA.

I tried adding these functions after acquiring and before releasing NFC in 3b19a51, but it triggers a furi_check (link) because both the RFID hardware (link) and the NFC hardware (link) try to use TIM1.