Remove downloader from NBI

[mbien]

• the download manager relied on suspend/resume/stop from java.lang.Thread which were deprecated since Java 1.2
• JDK 23 removes suspend/resume, others are already no-ops
• fixing this would require a completely different approach, and since NBI is no longer maintained and in the process to be replaced by nbpackage this is the easiest option

how to test: 1) setup JDK 23 2) checkout this branch 3) build (with zip):

ant clean -q
ant build -Dcluster.config=release

4) build installers (download installer.sh and run using bash)

bash installer.sh nbbuild/NetBeans-dev-dev-baa644f9077e618cb3555695e0d3f0a07a0db380-release.zip 42 121212

this should create the windows installer:

tree dist/
dist/
├── bundles
│   ├── Apache-NetBeans-42-bin-linux-x64.sh
│   └── Apache-NetBeans-42-bin-windows-x64.exe

which is now testable on windows (not testable on JDK 23ea since the native launcher can't parse ea java versions)

this PR would unblock https://github.com/apache/netbeans/pull/7525 (and https://github.com/apache/netbeans/pull/7484) full test on JDK 23 and nb-javac 23 ran in https://github.com/apache/netbeans/pull/7538 related to https://github.com/apache/netbeans/issues/4952

[mbien]

@matthiasblaesing tbh my first thought was also to try to reimplement it which I gave up on fairly quickly after going through the code. My second thought was to remove the time slicing scheduler and sequentialize the download to get rid of the suspend/resume at least. But since the threading model leaked through the API, this wouldn't really work (interrupts etc) - and testing this would have been a pain. Any modern downloader implementation would be trivial today but couldn't really be put behind that API.

@neilcsmith-net did also take a closer look through NBI long ago and also decided that it was not worth it, this is what spawned https://github.com/apache/netbeans-nbpackage as you know.

Last but not least: unmaintained net code isn't ideal, even if it would continue to work. We would keep releasing it even though all tests are disabled and nobody is looking at it anymore.

[mbien]

The check-for-updates checkbox has currently no purpose. It got enabled in https://github.com/apache/netbeans/pull/1348, wondering if we should turn it off again.

edit: will move other changes to separate PRs since the main purpose of this PR is to make NB buildable on JDk 23 edit2: -> https://github.com/apache/netbeans/pull/7550

[mbien]

I am planing to merge this relatively soon so that we can start building/testing on JDK 23. I tested this once more on win 10 (in conjunction with https://github.com/apache/netbeans/pull/7550) and saw no problems.

[mbien]

will rebase and then merge.

~once done, I will do the same with https://github.com/apache/netbeans/pull/7525, assuming everything there is still green (can't remember if it also requires nb-javac 23)~

edit: actually I believe the nb-javac PR is a precondition of the CI PR

[mbien]

lets wait with merge https://github.com/apache/netbeans/pull/7387#discussion_r1668389146 / https://github.com/apache/netbeans/pull/7553