[#2339] Reduce memory usage in ProtobufVarint32LengthFieldPrepender

Motivation:

Reduce memory usage in ProtobufVarint32LengthFieldPrepender.

Modifications:

Explicit set the buffer size that is needed for the header (between 1 and 5 bytes).

Result:

Less memory usage in ProtobufVarint32LengthFieldPrepender.