Add UserQuotaTracker to IpSecService

Add a small tracking object to enforce maximum
quotas for SPIs, Transforms, and Encap sockets. The
current quota limits are intentionally conservative
with the expectation that we can relax them more
easily than we can shrink them.

Bug: 37688603
Test: tbd
Change-Id: Iee59ac59ef9f4a7ab75a2e04f9ca72da82fc3229