Support IPsec packet loss detector

This CL creates an abstract class NetworkMetricMonitor and a
subclass IpSecPacketLossDetector. IpSecPacketLossDetector
is responsible for continuously monitoring IPsec packet loss
and reporting to the caller when the data loss rate surpass
a threshold. This detector allows the VCN to switch from
the underlying network that has bad quality.

This CL also defines new carrier configs that specify the
data loss threshold and detecting frequency

Bug: 282996138
Test: atest FrameworksVcnTests(new tests), CtsVcnTestCases
Change-Id: I5f4b8e1821bdbb37f0a6de6e1584f8e3c87273f3