[FTX Streaming] Orderbook check sums incorrect when using multiple treads

[douggie]

Currently the FtxStreamingAdapters is static, so is shared across mutliple threads, causing the check sum calculation (getOrderbookChecksum) to be shared. In a multi-threaded environment we want to ensure each thread has their own instance of the FtxStreamingAdapter.

I'll raise a PR accordingly.