Implement LINQ LeftJoin and RightJoin

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Closes #110292

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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.

[dotnet-issue-labeler]

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.

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Copilot reviewed 7 out of 14 changed files in this pull request and generated 2 comments.

Files not reviewed (7)

• src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csproj: Language not supported
• src/libraries/System.Linq/src/System.Linq.csproj: Language not supported
• src/libraries/System.Linq/tests/System.Linq.Tests.csproj: Language not supported
• src/libraries/System.Linq/ref/System.Linq.cs: Evaluated as low risk
• src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.cs: Evaluated as low risk
• src/libraries/System.Linq/tests/JoinTests.cs: Evaluated as low risk
• src/libraries/System.Linq.Queryable/tests/JoinTests.cs: Evaluated as low risk

Comments suppressed due to low confidence (3)

src/libraries/System.Linq/src/System/Linq/RightJoin.cs:43

• The IsEmptyArray method is not defined in the provided code. Ensure that this method is defined and works as expected.

if (IsEmptyArray(inner))

src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs:245

• The DynamicDependency attribute should be corrected to use the format: DynamicDependency(DynamicallyAccessedMemberTypes.PublicMethods, typeof(Enumerable)).

[DynamicDependency("LeftJoin`4", typeof(Enumerable))]

src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs:260

• The nullable type for q is not necessary. Use a simple cast instead: IQueryable q = source as IQueryable;

IQueryable<TSource>? q = source as IQueryable<TSource>;

The test case assumes that the default values for orderID and total are 0. It might be clearer to explicitly state that these are default values.

This comment was generated based on a coding guideline created by a repository admin.

The DynamicDependency attribute should be corrected to use the format: DynamicDependency(DynamicallyAccessedMemberTypes.PublicMethods, typeof(Enumerable)).

Suggested change

	[DynamicDependency("RightJoin`4", typeof(Enumerable))]
	[DynamicDependency(DynamicallyAccessedMemberTypes.PublicMethods, typeof(Enumerable))]