[Wi-Fi] Use new defined proto field for adding new networks panel page.

Use new metric, PANEL_ADD_WIFI_NETWORKS, for proto upload log use.

For R feature: Add a mechanism for apps to add saved networks to the
device, need to apply new metrics category.

Bug: 144891278
Test: Add following test case for testing metric:
      getMetricsCategory_shouldReturnPanelAddWifiNetworks()

Change-Id: I7cde8057c5f2b01c951b1de4203ab1c1a2f0f40a