Allow storing value field in binary format

[vitkutny]

DynamoDB has limited item size and its more efficient to store cacheed data in binary format. I have added opt-in argument $valueFieldBinary to not break BC.

We are using this together with custom CacheItemEncoderInterface:

• first encoder is using igbinary_serialize to serialize php structures into binary string
• second encoder takes this string and compresses these data further using GZ resulting again in binary string

Now we can use these together with $valueFieldBinary se to true