Log events at APF program generation

Example:
ConnectivityMetricsEvent(15:24:52.018, 0, 0): ApfProgramEvent(0/0 RAs 121B forever FLAG_MULTICAST_FILTER_ON)
ConnectivityMetricsEvent(15:24:53.036, 0, 0): ApfProgramEvent(1/1 RAs 334B 600s)
ConnectivityMetricsEvent(15:24:53.590, 0, 0): ApfProgramEvent(1/1 RAs 360B 600s FLAG_MULTICAST_FILTER_ON, FLAG_HAS_IPV4_ADDRESS)
ConnectivityMetricsEvent(15:24:58.157, 0, 0): ApfProgramEvent(1/1 RAs 294B 599s FLAG_HAS_IPV4_ADDRESS)

Bug: 28204408
Change-Id: I9c4c82861cf42eb2c7e7bf5471f05e8ff2fc560c