Extract `ReadBinaryFile()` and `WriteBinaryFile()` from `torcontrol.cpp` to its own `readwritefile.{h,cpp}` files, so that it can be reused from other modules.
This is a backport of [[https://github.com/bitcoin/bitcoin/pull/20685 | core#20685]] [1/20]
https://github.com/bitcoin/bitcoin/pull/20685/commits/4cba2fdafa483cbdb70f581174138ec253c80d48