.NET: Improve local release build perf by only formatting for one build target framework

[westey-m]

Motivation and Context

Currently when doing a release build locally, it runs dotnet format (target framework count) squared times, since it runs dotnet format for each target framework as part of the overall build, but dotnet format already formats for each target framework anyway.

All this only applies when run locally. This file does not apply when running on the build server, which already does this correctly.

Description

• Restricting dotnet format to only run for .net 10 builds.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Speeds up local Release builds by preventing dotnet format from running repeatedly for each target framework (while still skipping on GitHub Actions).

Changes:

• Updates the DotnetFormatOnBuild MSBuild target condition to only run on local Release builds for net10.0.
• Expands inline documentation to explain why formatting is restricted to a single TFM.