Support setting ApiParameterRouetInfo for endpoints

[captainsafia]

Contributes towards #36525.

The ApiExplorer for MVC populates each route parameter with an ApiParameterRouteInfo object that contains information about the constraints defined on a route parameter. This metadata can be used by OpenAPI libraries to generate more complete schemas for route parameters. This PR updates the ApiDescriptorProvider for endpoints to generate the same metadata.

Note: both Swashbuckle and NSwag don't currently respect the values in the RouteInfo property so there is some additional work to read from this info.

[halter73]

Are we worried about people casting and mutating this?

[captainsafia]

It's possible for someone to mutate this in a harmful way (say removing the constraints that we discovered). I don't anticipate this being common but it does't hurt to lock this down.

[pranavkm]

AsEnumerable doesn't do much though - https://source.dot.net/#System.Linq/System/Linq/Enumerable.cs,10. You would need to use AsReadOnly or ReadOnlyCollection if you truly want to lock this down.

But I'm of the shoot you own foot, now you have to go figure out how to bandage it school of thought. If somebody messes with the constraints and things don't work well, they're kinda at fault, no?

[captainsafia]

You would need to use AsReadOnly or ReadOnlyCollection if you truly want to lock this down.

Yep, to clarify by "it doesn't hurt to lock this down" I meant use AsReadOnly here as in 43fd3cd.

But I'm of the shoot you own foot, now you have to go figure out how to bandage it school of thought. If somebody messes with the constraints and things don't work well, they're kinda at fault, no?

Agreed, but it doesn't hurt to be explicit about the fact that we don't recommend doing things like this by making it read-only.