Feature: #73357 - Make thumbnail size in file browser configurable

See Issue #73357

Description

The default size of thumbnails in the file list is 64x64. These values can now be configured with UserTSConfig.

Example:

options.file_list.thumbnail.width = 256
options.file_list.thumbnail.height = 256

Impact

All preview images in the file list will be rendered in the configured thumbnail size.