Wifi: Add getConnectionCapabilities API

This commit adds the API for getConnectionCapabilities() in
ISupplicantStaIface HAL. This is used to return the Wifi support
for the connection on this STA interface.

Bug: 138634524
Bug: 140168755
Test: Manual
Test: VTS test
Change-Id: I24ff3c16434067e41491298e41041bdfdf06452a