Add @SensitiveData to ILockSettings.aidl

Use @SensitiveData on the binder interface of LockSettingsService to
ensure that lockscreen credentials do not get left around in the Parcel
data buffers.

Bug: 320392352
Bug: 416768837
Test: presubmit
Flag: EXEMPT not possible
Change-Id: I1c0841c4851543450a47b80e08c14ce38dc35e30