Sync similar elements Enclaves

[Wraith2]

A set of changes to being netcore and netfx closer to parity without changing functionality. Mostly reformatting to the same ruleset and then moving shared core to the shared location.

Observations:

1. netfx uses Cng classes directly but since Cng is the underlying implementation we could use the cross platform version on all targets without any change in functionality. I haven't done this but I think it's strongly worth considering.
2. I changed the CombineByteArrays function to two separate functions because the allocation of a byte[][] each time it was called bothered my optimization sensibilities.
3. a lot of the code dealing with hashes and keys could be made simpler using Memory refering to the the original blob if escape analysis proved the lifetimes were closed (and copies made if needed on a late bound basis) and if the code is used often enough for that to be worthwhile.