Refactor server/.../step_builder into pipeline/.../builder (#3967)

Extract the `step_builder` from the server to the pipeline package.
This cleans the interfaces / structure and will allow us to re-use it in the cli to correctly support pipeline execution (things like `depends_on` support).

Co-authored-by: Anton Bracke <anton.bracke@fastleansmart.com>
Co-authored-by: 6543 <6543@obermui.de>

cmd/server/openapi/docs.go

@@ -6046,6 +6046,9 @@ const docTemplate = `{
                 "name": {
                     "type": "string"
                 },
+                "org_id": {
+                    "type": "integer"
+                },
                 "owner": {
                     "type": "string"
                 },