RFR: 8345041: IGV: Free Placement Mode in IGV Layout [v6]

[Tobias Holenstein]

> This PR depends on https://github.com/openjdk/jdk/pull/22430. To check out this PR locally: 
> 
> git fetch https://git.openjdk.org/jdk.git pull/22438/head:pull/22438
> git checkout pull/22438
> 
> 
> Introduce a Free Placement Mode to IGV, allowing users to position nodes freely without being limited to the hierarchical layout constraints.
> 
> In this mode, users can manually drag and place nodes anywhere within the space, giving them complete control over the visual arrangement of the graph. Connections between nodes will be rendered as straight (or S curved) lines, without recalculating or enforcing hierarchical constraints.
> 
> This feature is ideal for users who need a flexible, non-restrictive way to organize and visualize complex graph structures in a customized and intuitive manner. The free placement of nodes will remain persistent until the layout is reset or another layout mode is selected.
> 
> ![free](https://github.com/user-attachments/assets/c150334e-4d9f-4abf-97ea-3cb42bd1c602)

Tobias Holenstein has updated the pull request incrementally with one additional commit since the last revision:

  layoutNode.setVertex(vertex) and  LayoutNode updateSize()

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22438/files
  - new: https://git.openjdk.org/jdk/pull/22438/files/66ad81f3..2847b60f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22438&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22438&range=04-05

  Stats: 20 lines in 2 files changed: 14 ins; 5 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22438.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22438/head:pull/22438

PR: https://git.openjdk.org/jdk/pull/22438