JetBrains: Move auth settings from project to application level config

Created by: vdavid

Context: Currently, we store our auth-related config with the project. Why: It was probably a quick decision years ago. Then we just never changed this.

Problem: For the user, it's inconvenient to set the auth settings for each project.

Solution:

Store them on the application level.

Settings that this change should affect:

• Sourcegraph URL
• Access token
• Default branch name
• Remote URL replacements
• isGlobbingEnabled

Settings that this change should not affect:

• lastSearchQuery
• lastSearchCaseSensitive
• lastSearchPatternType
• lastSearchContextSpec

We have existing users for the old version of the plugin, so migration is a question. Luckily, we access all settings through ConfigUtil, and a bit through SettingsConfigurable. We need to do is this:

• Add the five settings this change affects to the app-level config, then try accessing it at both places in ConfigUtil. SettingsConfigurable can access the values through ConfigUtil as well for reading, and write the values to the app-level config.

How to let them overwrite application settings on a project level in the future?