RFR: 8264795: IGV: Upgrade NetBeans platform

[Roberto Castañeda Lozano]

This change upgrades the NetBeans platform on which IGV is based to its latest version ([12.3](https://netbeans.apache.org/download/nb123/index.html)) and switches IGV's build system from Ant to Maven. The upgrade introduces support for a wide range of JDK versions (from 8 to 15, the latest version supported by NetBeans 12.3), and the switch from Ant to Maven makes the IGV build simpler, faster (first-time build is approximately 5x faster), and more stable (all dependencies are fetched directly from the Maven central repository).

The change also fixes broken unit tests in the Data module and runs them by default when building.

#### Testing

Regression-tested the following use cases manually on all combinations of (Linux, Windows, macOS) and (JDK 8, JDK 11, JDK 15):

- 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
- 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)

Thanks to Vladimir Ivanov for helping with testing on macOS.

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

Commit messages:
 - Update TemplatesAction name in layer file
 - Remove template integration test
 - Turn off schema validation, since the main input files are not specifying it anyway
 - Fix test errors
 - Configure Maven to run Data unit tests
 - Update copyright years of touched files
 - Indent all XML files consistently
 - Convert all files to UNIX format
 - Add copyright headers to Maven files
 - Remove unnecessary comments
 - ... and 35 more: https://git.openjdk.java.net/jdk/compare/011f6d13...11fb43fa

Changes: https://git.openjdk.java.net/jdk/pull/3361/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3361&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264795
  Stats: 5950 lines in 499 files changed: 2737 ins; 3110 del; 103 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3361.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3361/head:pull/3361

PR: https://git.openjdk.java.net/jdk/pull/3361