ResourceLoader and ResourceSaver should support serialization to in-memory string and/or byte arrays

[pakfront]

To support sending resources via RPC or other non-file methods, ResourceLoader and ResourceSaver should support serialization in-memory. For example:

void LoadAndSendMyResource(string resourceFilePath)
{
    _myResource = ResourceLoader.Load<MyResource>(resourceFilePath);
    Rpc(nameof(RPCReceiveResource), new Variant[] { ResourceLoader.ToBytes(myResource) });
}

[Rpc(MultiplayerApi.RpcMode.Authority, CallLocal = false, TransferMode = MultiplayerPeer.TransferModeEnum.Reliable)]
void RPCReceiveMyResource(byte [] bytes)
{
    _myResource = ResourceLoader.FromBytes<MyResource>(bytes);
}

If a byte array is considered dangerous due to injection risks, then strings might be safer, though it might limit the type of resource that can be sent.

void LoadAndSendMyResource(string resourceFilePath)
{
    _myResource = ResourceLoader.Load<MyResource>(resourceFilePath);
    Rpc(nameof(RPCReceiveResource), new Variant[] { ResourceLoader.ToString(myResource) });
}

[Rpc(MultiplayerApi.RpcMode.Authority, CallLocal = false, TransferMode = MultiplayerPeer.TransferModeEnum.Reliable)]
void RPCReceiveMyResource(string [] text)
{
    _myResource = ResourceLoader.FromString<MyResource>(text);
}