fix: Update path filters, test tags and backend processing (#6613)

* ✨ (tests): update tag value from "@starter-project" to "@starter-projects" for consistency across test files.

* 📝 (changes-filter.yaml): add new path "src/backend/base/langflow/custom/**" to starter-projects section
♻️ (changes-filter.yaml): remove path "src/backend/base/langflow/components/**" from components section and add it to starter-projects section
♻️ (changes-filter.yaml): add new path "src/backend/base/langflow/custom/**" to components section

* 🐛 (component.py): fix a bug where the status was not being returned when there is only one output in the component

* 🔧 (ci.yml): Expand path filter outputs for more comprehensive CI testing

* fix docstring placement

* ✨ (group.spec.ts): update click event modifiers to use "ControlOrMeta" for better cross-platform compatibility

* ✨ (changes-filter.yaml): add new directory "src/backend/base/langflow/graph/" to starter-projects for processing in the build pipeline.

* 🔄 Refactor graph data structures from sets to lists for performance and compatibility

* 🔧 Optimize RunnableVerticesManager predecessor checks and type hints

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Co-authored-by: Gabriel Luiz Freitas Almeida <gabriel@langflow.org>