Remove SqlExpressionVisitor from Cosmos

[roji]

Cleanup, continues #37533

[Copilot]

Pull request overview

Continues the cleanup from #37533 by removing the SqlExpressionVisitor base class from the Cosmos provider, inlining its VisitExtension dispatch logic directly into CosmosQuerySqlGenerator.

Changes:

• Deleted SqlExpressionVisitor.cs and changed CosmosQuerySqlGenerator to inherit from ExpressionVisitor directly
• Inlined the expression type dispatch switch into CosmosQuerySqlGenerator.VisitExtension, throwing with a descriptive error for unhandled expressions
• Changed all Visit* methods from protected override to protected virtual, and added a new UnhandledExpressionInVisitor resource string

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
SqlExpressionVisitor.cs	Deleted — base class no longer needed
CosmosQuerySqlGenerator.cs	Now extends ExpressionVisitor; inlines dispatch switch; methods become virtual
CosmosStrings.resx	Added UnhandledExpressionInVisitor resource string
CosmosStrings.Designer.cs	Auto-generated accessor for the new resource string (has a duplicate summary bug)

Files not reviewed (1)

• src/EFCore.Cosmos/Properties/CosmosStrings.Designer.cs: Language not supported

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[Copilot]

Pull request overview

This PR removes the SqlExpressionVisitor base class from the Cosmos provider, continuing the cleanup started in #37533 for the relational provider. The VisitExtension dispatch logic is inlined directly into CosmosQuerySqlGenerator, and unhandled expressions now throw with a descriptive error message.

Changes:

• Deleted SqlExpressionVisitor.cs and moved its dispatch switch into CosmosQuerySqlGenerator.VisitExtension
• Changed all Visit* methods from protected override to protected virtual and sealed override to protected virtual
• Added UnhandledExpressionInVisitor error string resource for Cosmos

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
SqlExpressionVisitor.cs	Deleted abstract visitor base class
CosmosQuerySqlGenerator.cs	Inlined VisitExtension dispatch; changed method modifiers from override/sealed override to virtual
CosmosStrings.resx	Added UnhandledExpressionInVisitor resource string
CosmosStrings.Designer.cs	Generated accessor for the new resource string

Files not reviewed (1)

• src/EFCore.Cosmos/Properties/CosmosStrings.Designer.cs: Language not supported

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