Immutable Piece Move providers

[rajat-g]

Instead of explicitly mentioning/creating ImmutableList every time in Test Helpers while creating Piece. This should be the logic of Piece that is it should copy the passed PieceMove Provider and should not leak reference from the getter method also.
That is:

A parameterized constructor should initialize all the fields performing a deep copy so that data members can’t be modified with an object reference.

Deep Copy of objects should be performed in the getter methods to return a copy rather than returning the actual object reference)