RFR: JDK-8290011: IGV: Remove dead code and cleanup [v20]

[Tobias Holenstein]

> Cleanup of the code in IGV without changing the functionality.
> 
> - removed dead code (unused classes, functions, variables) from the IGV code base
> - merged (and removed) redundant functions
> - added explicit position arguments to `layer.xml` - This avoids the position warning during building of IGV
> - ordered the inputs alphabetically, and used wildcards if >= 5 imports of a particular package
> - made class variables `final` whenever possible
> - removed `this.` in `this.funtion()` funciton calls when it was not needed
> - used lambdas instead of anonymous class if possible
> - fixed whitespace issues (e.g. double whitespace)
> - removed not needed copy of `RangeSliderModel tempModel` in `RangeSliderModel.java`
> - changed `EditorTopComponent` to take `InputGraph` as argument in constructor instead of `Diagram` and moved the creation of the `Diagram` to `DiagramViewModel.java` to increased encapsulation/modularity

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

  re-add ConnectionSet class
  
  is needed to highlight hovered edges

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10197/files
  - new: https://git.openjdk.org/jdk/pull/10197/files/d5044588..96425deb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10197&range=19
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10197&range=18-19

  Stats: 22 lines in 1 file changed: 14 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/10197.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10197/head:pull/10197

PR: https://git.openjdk.org/jdk/pull/10197