Remove BinFmt opt-in for un-exposed data transfers

[JanKrivanek]

Fixes #AB2263324

Context

Opting out of 17.10 changewave might lead to opting out of BinaryFormatter deprecation. This can unintentionally break ppl builds by breaking NodeConfig or TaskHost config de/serialization.
Both of the types and their data transfer is internal to MSBuild - there is no need to opt out from the safer, proprietary de/serialization. Hence let's prevent the opt out altogether.

Changes Made

Removed the opt-out option for NodeConfig and TaskHost config de/serialization

Testing

Existing tests