This commit adds two new auto-configuration classes for Spring GraphQL
support. Once the base GraphQL infrastructure is in place, we can now
expose the `GraphQlService` over an HTTP transport.
Spring GraphQL supports both MVC and WebFlux, so this commit ships with
one auto-configuration for each.
Developers can configure the HTTP path where the GraphQL resource is
exposed using the `spring.graphql.path` configuration property (this
defaults to `"/graphql"`).
See gh-29140
b38d04556e