Issue #1663206 by mortendk, aliyakhan, LewisNyman, Manuel Garcia, pakmanlh, rteijeiro, jwilson3: Update update.admin.css inline with our CSS standards

Issue #1996238 by sun, nod_, damiankloip, Wim Leers, longwave, alexpott, Xano, mdrummond, Mark Carver, Jeff Burnz, highrockmedia, joelpittet, et al: Replace hook_library_info() by *.libraries.yml file.