Add polyfills for Path.EndsInDirectorySeparator(...) and Path.TrimEndingDirectorySeparator(...)

[Tyrrrz]

No description provided.

[Copilot]

Pull Request Overview

This PR adds polyfills for Path.EndsInDirectorySeparator and Path.TrimEndingDirectorySeparator methods from .NET Core 3.0, making them available for earlier framework versions. Additionally, it includes refactoring improvements to existing code.

• Implements Path.EndsInDirectorySeparator to check if a path ends with a directory separator
• Implements Path.TrimEndingDirectorySeparator to remove trailing directory separators from paths
• Refactors Stream.ReadAtLeast and Stream.ReadAtLeastAsync to use the range operator instead of Slice method

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
PolyShim/NetCore30/Path.cs	Adds polyfill implementations for EndsInDirectorySeparator and TrimEndingDirectorySeparator with conditional compilation for different .NET Standard versions
PolyShim/NetCore10/RuntimeInformation.cs	Moves preprocessor directive to only wrap the IsOSPlatform method, allowing the class to be defined even when platform detection is unavailable
PolyShim/Net70/Stream.cs	Refactors buffer slicing to use idiomatic range operator syntax ([totalBytesRead..]) instead of .Slice() method
PolyShim.Tests/NetCore30/PathTests.cs	Adds comprehensive test coverage for the new Path polyfill methods including various path formats and edge cases

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[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 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 (ac078d6) to head (dbd293a).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@     Coverage Diff      @@
##   master   #39   +/-   ##
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