Add ability to configure borders in quick pick items list on plugin side

[vzhukovs]

What it does

This changes proposal adds ability to create quick open item configured with border and group label used in plugins.

When new terminal opens (mechanism used to create quick open items in extension):

When new task starts (mechanism used to create quick open items in plugin):

Signed-off-by: Vlad Zhukovskyi vzhukovs@redhat.com

How to test

Devfile to test changes: https://gist.github.com/vzhukovskii/23b275d18af208629648430df251a78e/raw/6451e1d0589cb435bf58208d560fb8006e338cd8/che-dev-workspace.yaml

Steps to test changes manually:

• clone che-theia and theia
• checkout to quick_pick_items_ext in che-theia and theia repo
• build che-theia, then go to dockerfile/theia and build docker image: ./build.sh --build-args:GITHUB_TOKEN=${GITHUB_TOKEN},THEIA_VERSION=master --tag:next --branch:quick_pick_items_ext --git-ref:refs\\/heads\\/quick_pick_items_ext --skip-tests
• use built docker image eclipse/che-theia:next as image for the main editor in che.

Need for: eclipse-che/che#13390
Linked Che-Theia PR: eclipse-che/che-theia#532

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[akosyakov]

code-wise looks good to me, have not tested though

[RomanNikitenko]

I'm going to test the changes tomorrow, sorry for delay.

[RomanNikitenko]

Tested the changes using proposed devfile: items are displayed with group label