Add API for VCN configuration of UDP port 4500 NAT Timeouts

This patch adds an API to allow VCN providers to configure the UDP port
4500 hint to improve the power implications of a VPN over the VCN.

Bug: 259000745
Test: atest FrameworksVcnTests
Change-Id: Id464ab43fa15d5f6a693f73932d95d9822320acb