[Contextual Edu] Check if device is connected before incrementing signal count

Only increment signal count when the target device is connected and passed the initial delay after setup.
e.g. As we will provide touchpad education for BACK gesture, only increment signal count when touchpad is connected and it is 72 hours after OOBE is launched or device is set up.

Bug: 362495235
Test: KeyboardTouchpadStatsInteractorTest
Flag: com.android.systemui.keyboard_touchpad_contextual_education
Change-Id: I8a40fc8386c0a3df729a1f6ac8f50255c2b311b8