Add polyfill for List<T>.EnsureCapacity(...)

[Tyrrrz]

No description provided.

[Copilot]

Pull request overview

This PR adds a polyfill for the List<T>.EnsureCapacity(int) method that was introduced in .NET 6.0, making it available for older .NET versions including .NET Core (pre-6.0), .NET Framework, and .NET Standard.

• Implements EnsureCapacity extension method with proper parameter validation
• Adds comprehensive test coverage for the new functionality
• Updates signature documentation with method count

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
PolyShim/Signatures.md	Updates total counts and documents the new List<T>.EnsureCapacity(int) API with link to official documentation
PolyShim/Net60/List.cs	Implements the polyfill extension method with negative capacity validation and capacity adjustment logic
PolyShim.Tests/Net60/ListTests.cs	Adds three test cases covering capacity increase, no-op when already sufficient, and negative parameter validation

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (80cb3b2) to head (276919e).
⚠️ Report is 108 commits behind head on master.

Additional details and impacted files

@@     Coverage Diff      @@
##   master   #47   +/-   ##
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