JetBrains: Audit <2022.1 functionality

Created by: philipp-spiess

While debugging an issue I tried starting 2020.2 and found numerous APIs that we use which aren't supported. Some of them are easy to fix, some of them required more work:

• We're using JCEF APIs that were added later but we can use deprecated APIs to work around the issue.
• The link implementation added for the code preview does not work.
• Maybe more areas? I did not get it to compile yet.