Cache IResult types for well known status codes and results without parameters

[davidfowl]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

We should optimize result allocation by caching common result instances (known status codes etc).

Describe the solution you'd like

Caching of these result types.

Additional context

No response

[brunolins16]

I have started look this issue and those are the status/results that I am planning to have a PR to cache:

Always cache:

• NoContentHttpResult : HTTP 204
• UnauthorizedHttpResult : HTTP 401
• EmptyResult: Already cached

Cache when no content (No parameters)

• OkObjectHttpResult : HTTP 200
• BadRequestObjectHttpResult : HTTP 400
• NotFoundObjectHttpResult : HTTP 404
• ConflictObjectHttpResult: HTTP 409
• UnprocessableEntityObjectHttpResult: HTTP 422

[davidfowl]

Also any know status code.

[brunolins16]

Also any know status code.

@davidfowl is this list good enough:

`Status200OK`
`Status204NoContent`
`Status400BadRequest`
`Status401Unauthorized`
`Status403Forbidden`
`Status404NotFound`
`Status409Conflict`
`Status412PreconditionFailed` 
`Status415UnsupportedMediaType`
`Status500InternalServerError`

Or, you want a cache for every known status code listed here (maybe it is too much 😂):
https://github.com/dotnet/aspnetcore/blob/main/src/Http/Http.Abstractions/src/StatusCodes.cs

I am planning to have an StatusCodeHttpResult cached instance for each of them, in addition to, what I mentioned before.

[davidfowl]

Everything in that class.

[halter73]

@davidfowl @brunolins16 Do you think we should codegen this? I'm not sure how much we do that kind of thing outside of Kestrel.

[brunolins16]

@halter73 I am benchmarking different ideas for the caching, but I have a feeling that it might be a good idea to codegen whatever idea we end up with.

[davidfowl]

Yes please t4?