Maven plugin download on startup ignores local repository splitting

### Apache NetBeans version

Apache NetBeans 18

### What happened

I added [`-Daether.enhancedLocalRepository.split=true`](https://maven.apache.org/resolver/local-repository.html#Split_Local_Repository) to NetBeans Options → Java → Maven → Global Execution Options and `MAVEN_OPTS` in `%userprofile%\.mavenrc`. When I build a project, dependencies are downloaded to the `cached` subdirectory in the local repository and the newly built artifact is put in the `installed` subdirectory. This is the desired behaviour.

However, when I remove everything from my local repository and simply start NetBeans, Maven plugins are downloaded into the root of the local repository:
```
$ find .
.
./org
./org/apache
./org/apache/maven
./org/apache/maven/plugins
./org/apache/maven/plugins/maven-clean-plugin
./org/apache/maven/plugins/maven-clean-plugin/3.2.0
./org/apache/maven/plugins/maven-clean-plugin/3.2.0/maven-clean-plugin-3.2.0.jar
./org/apache/maven/plugins/maven-clean-plugin/3.2.0/maven-clean-plugin-3.2.0.jar.sha1
./org/apache/maven/plugins/maven-compiler-plugin
./org/apache/maven/plugins/maven-compiler-plugin/3.10.1
./org/apache/maven/plugins/maven-compiler-plugin/3.10.1/maven-compiler-plugin-3.10.1.jar
./org/apache/maven/plugins/maven-compiler-plugin/3.10.1/maven-compiler-plugin-3.10.1.jar.sha1
./org/apache/maven/plugins/maven-dependency-plugin
./org/apache/maven/plugins/maven-dependency-plugin/3.6.0
./org/apache/maven/plugins/maven-dependency-plugin/3.6.0/maven-dependency-plugin-3.6.0.jar
./org/apache/maven/plugins/maven-dependency-plugin/3.6.0/maven-dependency-plugin-3.6.0.jar.sha1
./org/apache/maven/plugins/maven-deploy-plugin
./org/apache/maven/plugins/maven-deploy-plugin/3.1.0
./org/apache/maven/plugins/maven-deploy-plugin/3.1.0/maven-deploy-plugin-3.1.0.jar
./org/apache/maven/plugins/maven-deploy-plugin/3.1.0/maven-deploy-plugin-3.1.0.jar.sha1
./org/apache/maven/plugins/maven-enforcer-plugin
./org/apache/maven/plugins/maven-enforcer-plugin/3.3.0
./org/apache/maven/plugins/maven-enforcer-plugin/3.3.0/maven-enforcer-plugin-3.3.0.jar
./org/apache/maven/plugins/maven-enforcer-plugin/3.3.0/maven-enforcer-plugin-3.3.0.jar.sha1
./org/apache/maven/plugins/maven-install-plugin
./org/apache/maven/plugins/maven-install-plugin/3.1.0
./org/apache/maven/plugins/maven-install-plugin/3.1.0/maven-install-plugin-3.1.0.jar
./org/apache/maven/plugins/maven-install-plugin/3.1.0/maven-install-plugin-3.1.0.jar.sha1
./org/apache/maven/plugins/maven-jar-plugin
./org/apache/maven/plugins/maven-jar-plugin/3.3.0
./org/apache/maven/plugins/maven-jar-plugin/3.3.0/maven-jar-plugin-3.3.0.jar
./org/apache/maven/plugins/maven-jar-plugin/3.3.0/maven-jar-plugin-3.3.0.jar.sha1
./org/apache/maven/plugins/maven-javadoc-plugin
./org/apache/maven/plugins/maven-javadoc-plugin/3.5.0
./org/apache/maven/plugins/maven-javadoc-plugin/3.5.0/maven-javadoc-plugin-3.5.0.jar
./org/apache/maven/plugins/maven-javadoc-plugin/3.5.0/maven-javadoc-plugin-3.5.0.jar.sha1
./org/apache/maven/plugins/maven-site-plugin
./org/apache/maven/plugins/maven-site-plugin/3.12.1
./org/apache/maven/plugins/maven-site-plugin/3.12.1/maven-site-plugin-3.12.1.jar
./org/apache/maven/plugins/maven-site-plugin/3.12.1/maven-site-plugin-3.12.1.jar.sha1
./org/apache/maven/plugins/maven-source-plugin
./org/apache/maven/plugins/maven-source-plugin/3.3.0
./org/apache/maven/plugins/maven-source-plugin/3.3.0/maven-source-plugin-3.3.0.jar
./org/apache/maven/plugins/maven-source-plugin/3.3.0/maven-source-plugin-3.3.0.jar.sha1
./org/apache/maven/plugins/maven-surefire-plugin
./org/apache/maven/plugins/maven-surefire-plugin/3.1.0
./org/apache/maven/plugins/maven-surefire-plugin/3.1.0/maven-surefire-plugin-3.1.0.jar
./org/apache/maven/plugins/maven-surefire-plugin/3.1.0/maven-surefire-plugin-3.1.0.jar.sha1
./org/codehaus
./org/codehaus/mojo
./org/codehaus/mojo/build-helper-maven-plugin
./org/codehaus/mojo/build-helper-maven-plugin/3.4.0
./org/codehaus/mojo/build-helper-maven-plugin/3.4.0/build-helper-maven-plugin-3.4.0.jar
./org/codehaus/mojo/build-helper-maven-plugin/3.4.0/build-helper-maven-plugin-3.4.0.jar.sha1
./org/codehaus/mojo/versions-maven-plugin
./org/codehaus/mojo/versions-maven-plugin/2.15.0
./org/codehaus/mojo/versions-maven-plugin/2.15.0/versions-maven-plugin-2.15.0.jar
./org/codehaus/mojo/versions-maven-plugin/2.15.0/versions-maven-plugin-2.15.0.jar.sha1
```
They should be put into the `cached` directory instead.

### How to reproduce

Put `MAVEN_OPTS="-Daether.enhancedLocalRepository.split=true"` into your `~/.mavenrc` and add `-Daether.enhancedLocalRepository.split=true` to the Maven execution options in NetBeans. Remove everything from your local repository and start NetBeans.

### Did this work correctly in an earlier version?

No / Don't know

### Operating System

Windows 10 64 Bit

### JDK

OpenJDK 20.0.1

### Apache NetBeans packaging

Apache NetBeans binary zip

### Anything else

Maven 3.9.3

### Are you willing to submit a pull request?

No

Reproduce the startup behavior using the Maven execution options and ~/.mavenrc settings described in the issue, with an empty local repository. Trace the NetBeans Maven startup path that downloads plugins and compare it with a project build using local-repository splitting. Done means startup downloads place plugins under the cached subdirectory rather than the repository root.

Written by the indexing model from the issue text.