Approved API Proposal: #41614
Related change for directory creation method that takes an ACL: #41834 -merged and ported to 3.1 Prev2

Description
We have extension methods in System.IO.FileSystem.AclExtensions that let the user get and set ACLs for existing files, but we do not have methods that create files with predefined ACLs.
.NET ACL (Access Control List) support is Windows specific. This change will reside inside the System.IO.FileSystem.AccessControl assembly.

Customer impact
Before this change, customers had to create a file or filestream, then set its ACLs. This presents a few problems:

Potential security hole as files can be accessed between creation and modification.
Porting difficulties as there isn't a 1-1 API replacement
Stability issues with background processes (file filters) can prevent modifying ACLs right after creation (typically surfaces as a security exception).
This change addresses those problems by adding a new extension method that allows creating a file and ensuring the provided ACLs are set during creation.
This change is expected to be backported to 3.1.

* First commit

* Fix OperationCanceledException dependency error, revert nullable indication

* Only Directory files

* Unit tests verifications

* Split FileSystem.Windows into two additional files instead of one. Fix pinning.

* Remove dead comment, add actual UT verifications

* User WellKnownSidType

* Make method unsafe, nit comments addressed.

* Remove irrelevant comment

* Add additional exceptions to triple slash

* Add unit tests for additional exceptions

* Remove FileSystem.cs, it has one obsolete method. Replace all calls of that removed method.

* Second pass on required strings.resx resources

* Remove unused dependency cs files

* Move shared files to Common

* Add the missing braces

* Add nulcheck for this argument, add exception, document exception in triple slash, add unit test.

* Fix netstandard CI build failure

* Fix Microsoft.IO.Redist build issue with NetStandard

* Remove unnecessary assert in ut

* Fix build problem in Windows Packaging All Configurations x64_Debug, System.Runtime needs to be included to recognize NotNullIfNotNullAttribute, consumed in Path.Internal.cs

* Additional file splitting and dependency addition to fix netstandard/netfx build problems

* Fix netstandard and netcoreapp build issues

* Remove unused file

* nit cleaning

* Minimal unit tests

* Remove unused unit test code and spacing fix

* Add full framework condition to unit test

* Additional fix for full framework


Commit migrated from dotnet/corefx@5ed2e98

Approved API Proposal: dotnet/corefx#41614
Related change for directory creation method that takes an ACL: dotnet/corefx#41834 -merged and ported to 3.1 Prev2

Description
We have extension methods in System.IO.FileSystem.AclExtensions that let the user get and set ACLs for existing files, but we do not have methods that create files with predefined ACLs.
.NET ACL (Access Control List) support is Windows specific. This change will reside inside the System.IO.FileSystem.AccessControl assembly.

Customer impact
Before this change, customers had to create a file or filestream, then set its ACLs. This presents a few problems:

Potential security hole as files can be accessed between creation and modification.
Porting difficulties as there isn't a 1-1 API replacement
Stability issues with background processes (file filters) can prevent modifying ACLs right after creation (typically surfaces as a security exception).
This change addresses those problems by adding a new extension method that allows creating a file and ensuring the provided ACLs are set during creation.
This change is expected to be backported to 3.1.

Commit migrated from dotnet/corefx@508cbc4