RFR: 8279068: IGV: Update to work with JDK 16 and 17

[Roberto Castañeda Lozano]

This change upgrades the NetBeans Platform on which IGV is based to its latest version ([12.6](https://netbeans.apache.org/download/nb126/index.html)). The upgrade introduces support for JDK versions 16 and 17, and drops support for versions earlier than 11. The change adds a check to enforce that a supported JDK version is used when building IGV, emitting an informative error message otherwise.

#### Testing

Tested the following use cases manually on all combinations of (Linux, Windows, macOS) and (JDK 11, JDK 16, JDK 17):

- build
- open graph file (small.xml in [test-input.zip](https://bugs.openjdk.java.net/secure/attachment/93988/test-input.zip))
- import graphs via network (localhost)
- expand groups in outline
- open a graph
- open a clone
- zoom in and out
- search a node
- apply filters
- extract a node
- show all nodes
- select nodes corresponding to a bytecode
- view control flow
- select nodes corresponding to a basic block
- cluster nodes
- show satellite view
- compute the difference of two graphs
- change node text
- export graph as PDF
- remove a group
- save groups into a file
- open a large graph file (large.xml in [test-input.zip](https://bugs.openjdk.java.net/secure/attachment/93988/test-input.zip))
- open a large graph ("After Escape Analysis" in large.xml)

Also tested that building IGV on JDK 8 and 18 (EA) fails with the error message "IGV requires a JDK version between 11 and 17".

Thanks to Jesper Wilhelmsson for helping with testing on macOS.

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

Commit messages:
 - Pass all JVM options in a single line for Windows compatibility
 - Enforce JDK version
 - Update copyright years
 - Allow Netbeans Platform to break encapsulation (needed for correct behavior)
 - Simplify instructions
 - Update to latest Nashorn for compatibility with JDK 17
 - Update instructions
 - Update to latest NetBeans Platform version

Changes: https://git.openjdk.java.net/jdk/pull/7347/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7347&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279068
  Stats: 144 lines in 22 files changed: 121 ins; 0 del; 23 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7347.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7347/head:pull/7347

PR: https://git.openjdk.java.net/jdk/pull/7347