Fold inbox crypto into one assembly (#64307)

Fold inbox crypto into one assembly (#64307)

* Fold S.S.C.Csp into System.Security.Cryptography

This change leaves the tests in System.Security.Cryptography.Csp.Tests.dll,
because the crypto test infrastructure has not yet been upgraded to allow
for two algorithm provider tests in the same assembly (e.g. not both
Aes.Create() and AesCryptoServiceProvider can be tested)

* Change CryptoConfig string lookups to typeof for CSP types

* Fold S.S.C.Cng into S.S.Cryptography

* Fold S.S.C.OpenSsl into S.S.Cryptography

* Fold S.S.C.X509Certificates into S.S.Cryptography

* Fix dependent projects

* Fix ApiCompat errors

* Self-feedback

* Use typeof where now possible in CryptoConfig

* Don't use CNG's PKCS8 export for default EC objects

* RSA should probably function on Unix

* Fix nullability state of ChainPal.BuildChain across OSes

* Remove bad assert

* Special case macOS ECC data keys in CopyWithPrivateKey

* Undo some of the string resurrections

* Add missing Obsolete attribute