Create project validation route that allows you to specify project

The current project validation is fine if you only care about validating the config syntax. However, if you want to check it against the project settings, you have to specify a project, which the validation rest route does not support. We should add another project validation route that lets a project be specified and update the CLI command to optionally specify a project (or if possible, change the existing route to support the parameter). Other than the project ref validation, the remainder of the project validation should be identicla to the current route. If we go with creating a new REST route, we should make a ticket to eventually deprecate and remove the old route once people have had enough time to update their CLIs (to avoid maintaining two REST routes with very similar functionality).