Whitelist ConcurrentStack for concurrent collections

[Copilot]

System.Collections.Concurrent.ConcurrentStack<T> was blocked by the whitelist despite other concurrent collections being available, preventing users from using stack-based thread-safe data structures.

Changes

• Added ConcurrentStack* to BaseAccess.cs alongside ConcurrentBag, ConcurrentDictionary, and BlockingCollection

This enables standard concurrent stack operations in sandboxed code:

var stack = new ConcurrentStack<int>();
stack.Push(42);
stack.TryPop(out var result);
var count = stack.Count;

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Whitelist] System.Collections.Concurrent.ConcurrentStack<></issue_title>
<issue_description>### What it is?
```Compiler [1] SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack1' is not allowed when whitelist is enabled 10:06:44 Compiler [SB1000](https://sbox.game/dev/doc/code/code-basics/api-whitelist/) 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack1' is not allowed when whitelist is enabled
10:06:44 Compiler [1] SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack`1' is not allowed when whitelist is enabled
10:06:44 Compiler [1] SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack`1..ctor()' is not allowed when whitelist is enabled
10:06:44 Compiler SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack`1.Push( T )' is not allowed when whitelist is enabled
10:06:44 Compiler [1] SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack`1.Push( T )' is not allowed when whitelist is enabled
10:06:44 Compiler [1] SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack`1.TryPop( T& )' is not allowed when whitelist is enabled
10:06:44 Compiler SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack`1.TryPop( T& )' is not allowed when whitelist is enabled
10:06:44 Compiler [1] SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack`1.TryPop( T& )' is not allowed when whitelist is enabled
10:06:44 Compiler [1] SB1000 'System.Collections.Concurrent/System.Collections.Concurrent.ConcurrentStack`1.get_Count()' is not allowed when whitelist is enabled

### Why do you need to use this?

Sometimes we need ConcurrentStack for threading</issue_description>

<agent_instructions>Add to Sandbox.Access whitelist</agent_instructions>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes [Whitelist] System.Collections.Concurrent.ConcurrentStack<> #9933

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[Copilot]

Pull request overview

This PR adds ConcurrentStack<T> to the API whitelist for sandboxed code, enabling users to utilize thread-safe stack operations alongside the already-whitelisted concurrent collections (ConcurrentBag, ConcurrentDictionary, and BlockingCollection).

Changes:

• Added ConcurrentStack* wildcard pattern to the BaseAccess whitelist

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