[release/9.0] Add explicit conversion for value-type returning handlers with filters

[github-actions]

Description

Addresses #52128.

This PR fixes a bug with the handling of value type-returning handlers that are used in conjunction with endpoint filters. Such as:

var app = WebApplication.Create();

app
	.MapGet("/", () => { return 1; })
	.AddEndpointFilter(async (context, next) => await next(context));

app.Run();

This currently throws:

ArgumentException: Expression of type 'System.Int32' cannot be used for parameter of type 'System.Object' of method 'System.Threading.Tasks.ValueTask`1[System.Object] WrapObjectAsValueTask(System.Object)' (Parameter 'arg0')

Because the return type requires an explicit conversion before being wrapped as a ValueTask<object> to confirm with the EndpointFilterDelegate's signature.

Customer Impact

Without this bug fix, user applications that contain minimal API endpoints that return value types and use endpoint filters will fail to launch. Viable workarounds exist (for example, wrapping the value return in a Results.Ok), but they are difficult for the typical user to discover.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

Scope of impact is limited to minimal APIs + endpoint filters + compile-time code generation.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

[captainsafia]

Approved via email.

[captainsafia]

/azp run

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[captainsafia]

@BrennanConroy @amcasey Can I get a review here? This is the same as the changeset in the other branches.