* stopping fix: backend fixes for #836
- sets 'stopping' field on crawl when crawl is being stopped (both via db and on k8s object)
- k8s: show 'stopping' as part of crawljob object, update subchart
- set 'currCrawlStopping' on workflow
- support old and new browsertrix-crawler stopping keys
- tests: add tests for new stopping state, also test canceling crawl (disable test for stopping crawl, currently failing)
- catch redis error when getting stats
operator: additional optimizations:
- run pvc removal as background task
- catch any exceptions in finalizer stage (eg. if db is down), return false until finalizer completes