Update to ASP.NET Core 10 preview.6

[martincostello]

Update to the ASP.NET Core .NET 10 preview.6 and Microsoft.OpenApi 2.0.0-preview.29.

Notable changes

• Simplification of various namespaces to simply Microsoft.OpenApi.
• Interfaces reintroduced to various properties which simplifies the sorting, but breaks the ability to use collection expressions in a number of places.
• Some API diffs caused by ordering are reverted by serialization updates, so the diff post-merge should get smaller compared to the default branch again.

---

Needs updating to the official build, rather than a nightly, before merge.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.75%. Comparing base (c8e5aef) to head (080672c).
Report is 1 commits behind head on dotnet-vnext.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@               Coverage Diff                @@
##           dotnet-vnext    #3479      +/-   ##
================================================
+ Coverage         94.70%   94.75%   +0.05%     
================================================
  Files               110      110              
  Lines              3850     3830      -20     
  Branches            773      758      -15     
================================================
- Hits               3646     3629      -17     
+ Misses              204      201       -3     

Flag	Coverage Δ
Linux	94.75% <100.00%> (+0.05%)	⬆️
Windows	94.75% <100.00%> (+0.05%)	⬆️
macOS	94.75% <100.00%> (+0.05%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Copilot]

Pull Request Overview

This PR updates the project to ASP.NET Core 10 preview.6 and Microsoft.OpenApi 2.0.0-preview.29, simplifying various Microsoft.OpenApi namespaces to use the unified Microsoft.OpenApi namespace as per the notable changes mentioned in the description.

• Updates package references from preview.5 to preview.6
• Simplifies Microsoft.OpenApi namespace imports
• Adapts to breaking changes in the OpenApi library including loss of collection expressions support

Reviewed Changes

Copilot reviewed 146 out of 146 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Directory.Packages.props	Updates Microsoft.OpenApi packages to preview.29 and AspNetCore.OpenApi to preview.6
global.json	Updates .NET SDK version to 10.0.100-preview.6
src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/SwaggerGenerator.cs	Simplifies OpenApi namespace imports and removes collection expressions
test/WebSites/TestFirst.IntegrationTests/CreateUserTests.cs	Replaces collection expression with explicit SortedSet instantiation
Multiple test and source files	Simplifies OpenApi namespace imports from specific Models/Interfaces to unified namespace