[Epic] Route Groups

[halter73]

Now that the initial implementation of MapGroup has been merged, I'm closing the initial route grouping issue at #36007 and am using this "Epic" issue to track the remaining work for .NET 7.

• [Route Groups] Support AddFilter, WithOpenApi and other additive conventions #41427
• [Route Groups] WithTags et al. should target IEndpointConventionBuilder #41428
  [ ] [Route Groups] Add default metadata to endpoints exposing group structure #41429
• [Route Groups] Investigate link generation bug #41430
  [ ] [Route Groups] Implement IApplicationBuilder to support grouped middleware #41431
  [ ] [Route Groups] Investigate callback based API #41432
• [Route Groups] Rename GroupRouteBuilder to RouteGroupBuilder #41781

[rafikiassumani-msft]

Closing the issue. Will move the remaining items to .NET8 Planning.