Added support for EF Core 10 on .NET 10

[bkoelman]

This PR adds support for using Entity Framework Core 10 on .NET 10. Additionally, it adds support for OpenAPI 3.1.

Current limitations:

• No stable/unstable EF Core 10 provider for MySQL is available yet (so DapperExample fails to run)
  Upgrade to EF Core 10.0.0 PomeloFoundation/Pomelo.EntityFrameworkCore.MySql#2019
• No docfx release that is compatible with .NET 10 is available yet (currently runs binaries from our fork)
  chore: Add support for .NET 10 target framework dotnet/docfx#10859
• Tried to convert to .slnx, but reverted because code cleanup is not compatible yet
  https://youtrack.jetbrains.com/issue/RSRP-502346
• Builds are extremely slow (compiler bug); added workaround for Debug builds, but CI builds still take 4x longer
  Performance regression when running analyzers with .NET 10 dotnet/roslyn#80756
• Running Build.ps1 locally sometimes results in dotnet test exiting with error code

Unfortunately, coverage dropped quite a bit. This is because Microsoft.OpenAPI 2.x changed all collection properties to nullable, requiring callers to lazily initialize. This reduces runtime allocations, but also results in unreachable code where collections must be defensively initialized or null-checked, such as:

inlineSchemaForAttributes.Required ??= new SortedSet<string>(StringComparer.Ordinal)

and:

if (document.Components?.Schemas != null)

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• Adapted tests
• Documentation updated (version table in README.md)

[codecov]

Codecov Report

❌ Patch coverage is 88.78719% with 49 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.21%. Comparing base (ba3accf) to head (c211400).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...SchemaGenerators/Components/DataSchemaGenerator.cs	89.89%	0 Missing and 10 partials ⚠️
...le/SwaggerComponents/ResourceFieldSchemaBuilder.cs	81.57%	0 Missing and 7 partials ⚠️
...cuments/AtomicOperationsDocumentSchemaGenerator.cs	88.23%	0 Missing and 6 partials ⚠️
...rComponents/DocumentationOpenApiOperationFilter.cs	84.84%	0 Missing and 5 partials ⚠️
...buckle/SwaggerComponents/EndpointOrderingFilter.cs	60.00%	1 Missing and 3 partials ⚠️
...penApi.Swashbuckle/UnusedComponentSchemaCleaner.cs	81.81%	1 Missing and 3 partials ⚠️
...ators/Components/LinksVisibilitySchemaGenerator.cs	85.00%	0 Missing and 3 partials ⚠️
...ore.OpenApi.Swashbuckle/OpenApiSchemaExtensions.cs	91.66%	0 Missing and 2 partials ⚠️
...omponents/RelationshipIdentifierSchemaGenerator.cs	93.75%	0 Missing and 1 partial ⚠️
...tors/Components/RelationshipNameSchemaGenerator.cs	80.00%	1 Missing ⚠️
... and 6 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1853      +/-   ##
==========================================
- Coverage   92.80%   92.21%   -0.60%     
==========================================
  Files         437      437              
  Lines       14831    14866      +35     
  Branches     2392     2451      +59     
==========================================
- Hits        13764    13708      -56     
- Misses        654      713      +59     
- Partials      413      445      +32     

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