Add WifiKeystore to allow Wifi framework access legacykeystore

Add the WifiKeystore API for Wifi framework in mainline module,
to access the legacy keystore for Wifi private key blobs.

Bug: 205764502
Test: adb shell cmd wifi keystore
Change-Id: Ibe3f3d5611c8de26c2aa37b3b9dee49351cbe3c5
2 files changed