PDL: MsftReadSupportedFeaturesCommandComplete

Add event fields to MsftReadSupportedFeaturesCommandComplete to
derive prefix_length and prefix.

Add a new test testMsftReadSupportedFeaturesComplete for the event.

Bug: 246398494
Tag: #floss
Test: ./build.py --target test
Test: atest packages/modules/Bluetooth/system/gd/hci/hci_packets_test.cc
        x86_64 bluetooth_test_gd_unit: Passed: 26, Failed: 0,
                                       Ignored: 0, Assumption Failed: 0
Test: Manual test with next patch --
      "gd/hci: get MSFT opcode and read supported features"

Change-Id: Ic578d41ae80ec6a254a42759081dcd115cf59109