GD-Storage: Use ByteArray<16> instead of hci::LinkKey

* Create common::ByteArray<N>, a fixed size uint8_t array that
  supports FromString(), ToString() methods and is serializable
  and packet library parsable

Bug: 157533831
Test: atest bluetooth_test_gd
Tag: #gd-refactor
Change-Id: I3aabe8e3c0325da2e0f812a21f9779799ecae189