Move java task as a command

[mustard-mh]

Description

This PR makes gradle build not run by default, and instead you have to explicitly that you want to run by pressing enter
or setting environment variable RUN_GRADLE_TASK

Related Issue(s)

Related #9874

How to test

1. Open this PR in gitpod.io using https://gitpod.io/#https://github.com/gitpod-io/gitpod/pull/9927
2. You can see this prompt, and press enter will continue gradle build
   
3. Setting Environment Variables RUN_GRADLE_TASK for gitpod-io/gitpod repo
4. re open https://gitpod.io/#https://github.com/gitpod-io/gitpod/pull/9927
5. you will see gradle build is automatic start
   

Release Notes

NONE

Documentation

• /werft no-preview

[mustard-mh]

/werft run

👍 started the job as gitpod-build-hw-move-java.1
(with .werft/ from main)

[github-actions]

⚠️ Hey reviewer! BE CAREFUL ⚠️
Review the code before opening in your Gitpod. .gitpod.yml was changed and it might be harmful.

[felladrin]

Looking good!

When the workspace starts, du -d 1 -h /workspace outputs the following:

About 3 minutes later after Pressing Enter, the Java task completes:

And this is the result of du -d 1 -h /workspace after it:

I think the exchange of 5.9GB in prebuilds for 3 minutes after the IDE starts is worth it, considering that even who develops the JetBrains IDEs Plugins will somtimes want to skip this task.

[akosyakov]

lgtm

[felladrin]

I've also noticed the workspace loading faster, when opening this PR.

And when using RUN_GRADLE_TASK to automatically start the task, it was all ready 2 minutes after the IDE finished loading (due to the command start executing before the IDE shows up).