Observable Preferences Y (Resetting preferences)

[calixtus]

Refs #12655 (Importing into a present, observable and mutable preferences object)

Refs #10177 (Cleaning up dependencies to prefs)
Refs #12990 (Cleaning up JabRefGuiPreferences / JabRefCliPreferences
Follow up to #10002

Steps to test

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• [.] I manually tested my changes in running JabRef (always required)
• [.] I added JUnit tests for changes (if applicable)
• [.] I added screenshots in the PR description (if change is visible to the user)
• [.] I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• [.] I checked the user documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.

[koppor]

Related (because language dependent): #13901

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨

[koppor]

Prototype for workspace preferences - needs to be continued for the other preferences.

We prepared the UI under the assumption that the adaption will be done soon.

[koppor]

Strange that following string still apperas:

- "You must restart JabRef for this to come into effect."

[calixtus]

Strange that following string still apperas:

- "You must restart JabRef for this to come into effect."

Fixed. Was about a duplicated property in WorkspacePreferences that was removed.

[koppor]

No CHANGELOG.md yet, because issue #12655 not fixed.

The behavior of removing the warning message is too little.

[calixtus]

Working pattern for followup PRs:
In JabRefGui/CliPreferences remove

In XXXPreferences class

• Add private default constructor

• Add getDefault method

• Add setAll method

In JabRefGui/CliPreferences class

• Add fromBackingStore method

• Modify getXXXPreferences method

• Add to clear / importPreferences method

[calixtus]

Should be renamed in followup to "getWorkspacePreferencesFromBackingStore"