Labeled break and continue Statements

• Specification: https://github.com/dotnet/csharplang/blob/main/proposals/labeled-break-continue.md
• Discussion: [Proposal]: Labeled `break` and `continue` Statements #9876

Summary

Allow break and continue statements to optionally specify a label that identifies which loop or switch
statement to target, enabling cleaner control flow in nested constructs without requiring goto statements.

For example:

```csharp
outer: for (int x = 0; x < xMax; x++)
{
    for (int y = 0; y < yMax; y++)
    {
        if (ShouldSkipRest(x, y))
            continue outer;
        
        if (ShouldExitAll(x, y))
            break outer;
    }
}

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