Unhiding HttpProxy accessors in WifiConfiguration. This change occurs in parrallel with changes that restrict updating of WifiConfigurations with new or updated proxy info to uids holding permission OVERRIDE_WIFI_CONFIG, or holding DeviceOwner or ProfileOwner policies. Bug: 14669153 Test: None Change-Id: Id69525cfec152ea52697693f9a3bd6f86019c694 Merged-In: Id69525cfec152ea52697693f9a3bd6f86019c694