RFR: 8265125: IGV: cannot edit forms with NetBeans GUI builder

[Roberto Castañeda Lozano]

This change moves all NetBeans-generated .form files to the same directory as their corresponding Java source files. This allows NetBeans to recognize the corresponding Java source files as Swing forms, and open them in "Design" mode:

![design](https://user-images.githubusercontent.com/8792647/114543087-07187d80-9c59-11eb-8d30-6d53db35db17.png)

The .form files are only processed by NetBeans, so this change does not affect how IGV is built and run.

Tested manually by reproducing the steps in the [JBS bug report](https://bugs.openjdk.java.net/browse/JDK-8265125) and by checking that IGV can be built and run following the steps in IGV's [README.md](https://github.com/openjdk/jdk/tree/master/src/utils/IdealGraphVisualizer#building-and-running) file.

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Commit messages:
 - Move NetBeans .form files to Java directories

Changes: https://git.openjdk.java.net/jdk/pull/3461/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3461&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265125
  Stats: 0 lines in 7 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3461.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3461/head:pull/3461

PR: https://git.openjdk.java.net/jdk/pull/3461