Expose SecurityDescriptor as protected (dotnet/corefx#38283)

Expose SecurityDescriptor as protected (dotnet/corefx#38283)

* Expose SecurityDescriptor as protected

Classes derived from ObjectSecurity depended on seeing the _securityDescriptor field, which is marked internal. Internal visibility no longer works as types have split into different assemblies and is causing failures, such as dotnet/corefx#35993.

This change also ran the UpdateVSConfigurations target on the changed libraries.

* Address feedback

Commit migrated from https://github.com/dotnet/corefx/commit/7570445805fe57966ff6494fcd582de8b79088a0