Make http(s) URIs their own module key (#495)

GenericUrl is a catch-all that uses URL.openConnection().
Since we now have special handling of HTTP urls, it makes more sense to
put it in its own module key.

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/CliCommand.kt

@@ -164,6 +164,7 @@ abstract class CliCommand(protected val cliOptions: CliBaseOptions) {
       add(ModuleKeyFactories.projectpackage)
       addAll(ModuleKeyFactories.fromServiceProviders())
       add(ModuleKeyFactories.file)
+      add(ModuleKeyFactories.http)
       add(ModuleKeyFactories.genericUrl)
     }
   }