Add local log

This change adds a local log buffer to the VcnManagementService,
ensuring that if the system-wide log buffer saturates, some basic VCN
logs are retained

Bug: 188842647
Test: atest FrameworksVcnTests
Test: adb shell dumpsys vcn_management
Change-Id: Ib250e38fc5a034a6d2a327b2ee159e7186a15ada