Update performance notes for SetParametersAsync method

[guardrex]

Fixes #35507

Thanks @hakenr! 🎷

Wade/Tom ... Just need one review to get this one in.

Clarified the performance improvement potential of overriding SetParametersAsync, noting it typically yields under 10% improvement in .NET 10.

Notes ...

• I'm using the HTML named entity for the em dash because the GH markdown editor doesn't make it clear that the character is indeed an em dash.
• I'm going to peg the "current release" remark at .NET 10 because we don't know how this might change in the future and the "current release" could be anything when the content targets >=8.0. Benchmark testing was performed for .NET 10, so we can only state the figures for that release.
• This must be versioned because "Interactive Server" has no meaning prior to .NET 8.

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Internal previews

📄 File	🔗 Preview link
aspnetcore/blazor/performance/rendering.md	aspnetcore/blazor/performance/rendering

[Copilot]

Pull request overview

Updates the Blazor rendering performance guidance to clarify the (reduced) benefit of manually overriding SetParametersAsync in newer ASP.NET Core/Blazor versions.

Changes:

• Adds monikered guidance for >= aspnetcore-8.0 that characterizes the typical performance gains as small (benchmarked on .NET 10).
• Retains the prior (larger) performance improvement guidance for < aspnetcore-8.0.

[guardrex]

Sorry for all of the update pings, @hakenr. The lingo is a bit tricky. I think I have it now ... or close to what we'll go with. Please feel free to suggest updates. Wade or Tom will be along shortly to review, and then we'll get this merged. Thanks again!

[hakenr]

lgtm

[wadepickett]

Looks great, approved.