[WIP] The PowerShell extension-related fixes

[azatsarynnyy]

Signed-off-by: Artem Zatsarynnyi azatsary@redhat.com

What does this PR do?

1. Terminals:

• Returns back the VS Code built-in terminal with all its features enabled (e.g. Shell integration, contributed Terminal Profiles, etc.).
• Contributes "opening a terminal to any DevWorkspace container" feature exclusively by the VS Code extension API, without the VS Code internals modifications.

2. Tasks:

• All the functionality related to running the Devfile Commands plugged into VS Code through the extensions.
  The che-commands extension relies on the che-terminal extension's API for running the Devfile Commands in any container via the machine-exec server.
• Returns back the possibility of running any non-Che VS Code Tasks, but not Che Tasks (Devfile Commands) only.

3. Terminal-related changes removed obstacles that prevented the PowerShell VS Code extension from working properly.
   See more details in the comment PowerShell VS Code extension failed to start eclipse-che/che#21626 (comment).

What issues does this PR fix or reference?

• Implement a VS Code extension for opening the container terminals eclipse-che/che#21673
• PowerShell VS Code extension failed to start eclipse-che/che#21626
• It's not possible to run a Task in Che-Code if it's not che type eclipse-che/che#21466
• Enabling the extended Shell integration breaks the auto-opened terminal in Che-Code eclipse-che/che#21616

How to test this PR?

Test opening the terminals

Use case 1: there're multiple contributed containers

1. Start a DevWorkspace with the test project https://github.com/azatsarynnyy/java-spring-petclinic/tree/trm-ext-multiple
2. In the Command Palette, call the command Terminal: Create New Terminal to DevWorkspace Container.
3. VS Code should ask to choose a container as there're several contributed containers except for the editor's container.

Use case 2: there's one contributed container (except for the editor's container)

1. Start a DevWorkspace with the test project https://github.com/azatsarynnyy/java-spring-petclinic/tree/trm-ext
2. In the Command Palette, call the command Terminal: Create New Terminal to DevWorkspace Container.
3. VS Code should not ask to choose a container as there's a single contributed container (mariadb) except the editor's container.
4. VS Code should open a terminal to the container mariadb.

Use case 3: there're no contributed containers (except for the editor's container)

In this case, the behavior should be exactly the same as opening a built-in VS Code terminal.

1. Start a DevWorkspace with the test project https://github.com/azatsarynnyy/java-spring-petclinic/tree/trm-ext-0
2. In the Command Palette, call the command Terminal: Create New Terminal to DevWorkspace Container.
3. VS Code should not ask to choose a container as there're no contributed containers except for the editor's container.
4. VS Code should open a terminal to the editor container tools.
5. Check that the opened terminal is a full-featured built-in terminal, not the machine-exec terminal. They differ in that the machine-exec terminal doesn't support features like Shell integration.

Test running the tasks

1. Start a DevWorkspace with the test project https://github.com/azatsarynnyy/java-spring-petclinic/tree/trm-ext
2. Create test tasks.json with a shell task. E.g.: Terminal > Configure Tasks... > Create tasks.json file from template > maven.
3. Run the shell task.
4. The task should be executed as expected. It shouldn't hang as described in It's not possible to run a Task in Che-Code if it's not che type eclipse-che/che#21466

Test PowerShell extension functionality

1. Start a DevWorkspace with the test project https://github.com/azatsarynnyy/PowerShellEditorServices/tree/trm-ext.
2. Install the recommended PowerShell extension.
3. Make sure a new Terminal Profile pwsh is contributed to the Launch Profile... menu.
4. After activating the extension (e.g. on opening a *.ps1 file), a new terminal PowerShell Extension is launched automatically.
5. Check the editor autocompletion in the *.ps1 file work as expected.
6. Check that the PowerShell left-side panel is populated with the commands.
7. Check that no problems are reported in the extension's logs (View>Output).

[azatsarynnyy]

This PR is superseded by #122, #123, #124