RFR: 8268768: idea.sh has been updated in surprising and incompatible ways

[Maurizio Cimadamore]

As the title says (please also refer to the JBS issue which describes all the issues in more details), the IDE support for IntelliJ has been updated with many enhancements as part of a seemingly innocuous "path handling" fix. The IDE doesn't appear to be usable in the same way it was in the past and many functionalities have been broken as a result (including support for jtreg test execution using the plugin).

For the above reasons, I'm reverting the plugin and idea.sh code to last known working version. Any _targeted_ fix can be re-applied after the revert. Larger enhancements need to be discussed in the proper venue:

https://openjdk.java.net/groups/ide-support/

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Commit messages:
 - Revert idea.sh
 - Revert idea support changes

Changes: https://git.openjdk.java.net/jdk/pull/4492/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4492&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268768
  Stats: 690 lines in 12 files changed: 492 ins; 63 del; 135 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4492.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4492/head:pull/4492

PR: https://git.openjdk.java.net/jdk/pull/4492