[FSSDK-11837] legacy api adjustment with key null support in decide#388

junaed-optimizely merged 3 commits intomasteroptimizely/csharp-sdk:masterfrom

junaed/fssdk-11837-key-null-decideoptimizely/csharp-sdk:junaed/fssdk-11837-key-null-decideCopy head branch name to clipboard