[JetBrains] Avoid shutting down terminals when closing the client

[felladrin]

Description

This PR changes the following:

• Avoid shutting down terminals when closing JetBrains Client.
• Open terminals for each Gitpod Task Terminal running and close them when JetBrains Client gest closed. We need to do this because clicking "Disconnect" is different from clicking "X" button from JetBrains Client Window [1]. Now the terminals are behaving the same as in VS Code.
• Replace the use of application.executeOnPooledThread (thread) with lifetime.launch (coroutine).

About the changes

Making the GitpodTerminalService class extend Disposable opens doors for us to use the defineNestedLifetime() method inside the class.
This method creates a LifetimeDefinition that is automatically terminated whenever the class is disposed.
GitpodTerminalService is created when a Controller Client connects and disposed when the client disconnects.
The LifetimeDefinition also allow us to launch coroutines (via launch method), and these coroutines are automatically terminated when the lifetime terminates.
This allows us to rely on the lifetime life-cycle to avoid running something in case the Controller Client disconnects.
For example: If we do the following, <some_task> won't be executed if the lifetime is terminated within 5 seconds after the coroutine is launched:

lifetime.launch {
    delay(5000)
    <some_task>
}

We currently have no way to know if a terminal widget was closed manually by the user or if it was closed due to the user closing JetBrains Client [1], so this allows us to prevent <some_task> [shutting down Gitpod Task Terminals, in our case] from running if JetBrains client has been closed. Gitpod Task Terminals are only shut down if the user clicks the "X" button in the terminal widget.

Related Issue(s)

• Resolves [JetBrains] Task should be stopped when closing terminal tab #12126

How to test

1. Open the preview environment of this PR and select Stable IntelliJ IDEA as your editor.
2. Start a new workspace from Gitpod's Repository, which has 5 terminals opened when it starts.
3. Close JetBrains Client by clicking "X" button.
4. Reconnect to the workspace and confirm if all the terminals remain open. Repeat it 3 times to ensure they never get closed unless you click "X" button on the terminal widget. (You can also use gp tasks list to know if Gitpod Terminals are in the "running" state)

Release Notes

Fixed an issue which caused Gitpod Terminals to be terminated when closing JetBrains Client.

Werft options:

• /werft with-local-preview
  If enabled this will build install/preview
• /werft with-preview
• /werft with-large-vm
• /werft with-integration-tests=all
  Valid options are all, workspace, webapp, ide, jetbrains, vscode, ssh

[andreafalzetti]

/werft run recreate-preview

👍 started the job as gitpod-build-felladrin-avoid-shutting-down-terminals-whena.5
(with .werft/ from main)

[andreafalzetti]

Reviewed and tested, works as expected ✅

/hold

Unhold when you're ready