Closes #11840

Change under libraryproperties

• Implemented validateDirectory method to check if a directory exists and is valid.
• Added validateAndShowError method to display error messages for invalid statuses.
• Updated validateSettings method to validate multiple directory statuses and show errors if any.
• Initialized visualizers error icon for library-specific, user-specific, and LaTeX file directories.

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• Change in CHANGELOG.md described in a way that is understandable for the average user (if change is visible to the user)
• [/] Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (if change is visible to the user)
• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• Checked 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 to the documentation repository.