[RTT] Legacy RTT API: add attempted/succeeded counts

Wi-Fi RTT legacy API is (now) a wrapper around the new API. Two
new result parameters were added to the new API but not propagated
to the corresponding legacy API:

- Count of attempted measurements
- Count of successful measurements

Bug: 79883720
Test: unit tests
Test: RangeApSupporting11McTest:test_legacy_rtt_80211mc_supporting_aps
Change-Id: Id000c691c22319474e3e98f5ba5d77e4bb4c343e