Add InlineArrayX types

[333fred]

Description

Closes #111973. Implements the API as proposed.

[ghost]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[ghost]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[Copilot]

Pull Request Overview

This PR introduces a set of InlineArrayX types (from InlineArray2 to InlineArray15) as proposed to support optimized inline array storage.

• Added new InlineArrayX structs in both implementation and reference assemblies
• Added tests verifying element assignment and access across the new inline array types

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Runtime/CompilerServices/InlineArrayTests.cs	Added tests covering basic indexing operations for each InlineArray type
src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/InlineArray.cs	Implemented InlineArrayX structs with the InlineArray attribute
src/libraries/System.Runtime/ref/System.Runtime.cs	Updated reference definitions to include the new InlineArrayX types

Comments suppressed due to low confidence (1)

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Runtime/CompilerServices/InlineArrayTests.cs:12

• Consider adding tests for out-of-range index access to ensure that the InlineArray types throw appropriate exceptions or handle invalid indices as expected.

public void InlineArray2Test()

[stephentoub]

Thanks

[stephentoub]

Thanks

[stephentoub]

/ba-g net timeouts