Move SecHub plugins code from dedicated repositories to the SecHub repository

[winzj]

ToDos

1. The code of all SecHub plugins shall be moved into the SecHub repository
2. The existing SecHub plugins repositories will not be deleted
3. The existing SecHub plugins repositories can be used for issue tracking
   -> The eclipse plugin repository additonally contains the artifacts in update-site as binaries
4. A README.adoc shall be added to each plugin repositories that will link to the plugin code inside the SecHub repository code. This README.adoc contains the information, that the issue tracking is still done inside the dedicated plugin repository.

Plugin file structure inside the SecHub repository

/gradlew.sh
/sechub-server-core/
/ide-plugins
     /eclipse
        /src/main/java
     /jetbrains
     /vscode

Solution

• move https://github.com/mercedes-benz/sechub-plugin-intellij
• move https://github.com/mercedes-benz/sechub-plugin-vscode
• move https://github.com/mercedes-benz/sechub-plugin-eclipse
• exclude ide-plugins form the normal Sechub Java build workflow.