Implement runtime-based IValidatableTypeInfoResolver for minimal API validation

[Copilot]

This PR implements a runtime implementation of IValidatableTypeInfoResolver to enable minimal-API validation when the source-generator path is unavailable (e.g., dynamic compilation, IDEs without generators, or environments where generators are turned off).

Background

Previously, the validation system had:

• ✅ Compile-time story: Microsoft.AspNetCore.Http.ValidationsGenerator source-generator for AOT-friendly static lookups
• ✅ Runtime parameter discovery: RuntimeValidatableParameterInfoResolver for method parameters
• ❌ Runtime type discovery: TryGetValidatableTypeInfo was a stub that always returned false

This left a gap where validation wouldn't work in dynamic scenarios without the generator.

Implementation

Core Components

RuntimeValidatableTypeInfoResolver - Main resolver class that:

• Uses reflection to walk public instance properties recursively
• Builds ValidatableTypeInfo graphs that mirror compile-time generator output
• Handles validation attributes like [Required], [Range], [Display], etc.

Cycle Prevention & Performance:

• HashSet<Type> tracking during discovery prevents infinite recursion (A ↔ B references)
• ConcurrentDictionary<Type, IValidatableInfo?> for thread-safe caching
• Skips primitives, enums, strings, DateTime (same logic as parameter resolver)

Registration:

• Added to ValidationOptions.Resolvers in AddValidation()
• Placed after parameter resolver but before user-added fallbacks
• Generated resolvers still take precedence when available

Example Usage

// Works without source generators now!
public class Person
{
    [Required]
    [StringLength(50)]
    public string Name { get; set; } = string.Empty;

    [Range(0, 120)]
    public int Age { get; set; }

    public Address Address { get; set; } = new();
}

public class Address  
{
    [Required]
    public string City { get; set; } = string.Empty;
}

// Validation now works at runtime
services.AddValidation();
// Validates nested objects, collections, handles cycles automatically

Testing

• 11 unit tests covering primitives, complex types, collections, cycles, caching
• 4 integration tests verifying service registration and resolver ordering
• Manual verification with real POCOs and validation scenarios

All tests pass and validate the expected behavior matches the original issue requirements.

Fixes #61220.

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[dotnet-policy-service]

Greetings human! You've submitted a PR that modifies code that is shared with https://github.com/dotnet/runtime . Please make sure you synchronize this code with the changes in that repo!

[captainsafia]

@copilot Update the RuntimeValidatableTypeInfoResolverTests tests to use the validatable info types returned by cases that support them to validate actual test data.

[Copilot]

@copilot Update the RuntimeValidatableTypeInfoResolverTests tests to use the validatable info types returned by cases that support them to validate actual test data.

Updated the RuntimeValidatableTypeInfoResolverTests to use the returned validatable info objects to validate actual test data. The tests now verify validation behavior with both valid and invalid data scenarios, ensuring the runtime resolver works correctly in practice. Commit ee9c087

[dotnet-policy-service]

Looks like this PR hasn't been active for some time and the codebase could have been changed in the meantime.
To make sure no conflicting changes have occurred, please rerun validation before merging. You can do this by leaving an /azp run comment here (requires commit rights), or by simply closing and reopening.