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