Move database cache rebuild to a background task with polling (13)#18922

Migaroez merged 5 commits intov13/devumbraco/Umbraco-CMS:v13/devfrom

v13/task/backport-long-running-database-rebuild-operation-to-submit-and-pollumbraco/Umbraco-CMS:v13/task/backport-long-running-database-rebuild-operation-to-submit-and-pollCopy head branch name to clipboard