Rename getCapabilities to getFeatureSet

in IWifiChip and IWifiStaIface.

Main purpose is to distinguish between
the 2 capability methods in IWifiChip:
 - getCapabilities (renamed here)
 - getWifiChipCapabilities

Bug: 267819850
Test: atest VtsHalWifiChipTargetTest \
            VtsHalWifiStaIfaceTargetTest
Change-Id: I03c15d652d02aef99b219c2d630b69acb4d9e43c