Revert "Revert "AP_HAL: add force_safety_on method""

This reverts commit db129f4d715ec07c83c82e8169c43d77da7210b6.
Revert "Revert "HAL_PX4: implement force_safety_on""

This reverts commit 2f16fc80ffa7a7eec3e7efc112b6c4a59d0c4573.
Revert "Revert "HAL_VRBrain: implement force_safety_on""

This reverts commit 63e794a5ea18696dcec545a26fd7da22e9d0ce7a.