Rename resolver files from dot to underscore separation

Change gqlgen filename_template from {name}.resolvers.go to
{name}_resolvers.go across all three APIs for consistent Go naming.

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/server/api/connect/v1/gqlgen.yaml

@@ -14,7 +14,7 @@ resolver:
   layout: "follow-schema"
   dir: "."
   package: "connect_v1"
-  filename_template: "{name}.resolvers.go"
+  filename_template: "{name}_resolvers.go"
 
 autobind: []
 call_argument_directives_with_null: true