[CDAP-14284] Adds base implementation to handle different types of nodes in React
- Modifies Default Node to resemble SourceNode
- Avoids DAGRenderer to repaint everything on each node manipulation
- Modifies raw styles to css-in-js to start with
- Extracts generic node functionalities to utilitites module
- Adds Source, Transform, Sink Error, Sink & Alertpublisher nodes
- Modifies AbstractNode to handle nodes with alert and error endpoints
- Modifies Source & Transform nodes based on modifications to AbstractNode
- Modifies DAGRenderer to delegate incoming connection validation function to individual nodes
- Adds boolean options to show/hide alert and error endpoints in transform nodes
