Add ability to manually move nodes in Graph View

### Description

Sometimes, the Graph View for a DAG can be difficult to digest based on the spacing of nodes (Tasks, Sensors, Task Groups, etc). Being able to manually re-arrange nodes (of course, without changing dependencies) would make this experience better.

### Use case/motivation

Provide DAG Authors/Viewers a better experience for using Graph View. **I think one of the important things to keep in mind is that this is NOT the ability to manually change dependencies. Just a way to change how the graph is visualized.

### Related issues

NA

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

Start by locating the Graph View entry point and its existing graph-layout behavior. Review how nodes, including Tasks, Sensors, and Task Groups, are rendered and verify that manual repositioning changes only visualization layout, never DAG dependencies.

Written by the indexing model from the issue text.