wifi: rtw89: advertise missing extended scan feature

Add support for random serial number in probe request and
configure channel dwell time. Advertise corresponding feature flag
NL80211_EXT_FEATURE_SCAN_RANDOM_SN and NL80211_EXT_FEATURE_SET_SCAN_DWELL.
Use the scan request duration as channel dwell time when it is
non-zero, otherwise use the default value.

Signed-off-by: Kuan-Chung Chen <damon.chen@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240222064258.59782-2-pkshih@realtek.com