* Various changes to try to ensure that fewer goroutines survive after a test completes:
* add Core.ShutdownWait that doesn't return until shutdown is done
* create the usedCodes cache on seal and nil it out on pre-seal so that the finalizer kills the janitor goroutine
* stop seal health checks on seal rather than wait for them to discover the active context is done
* make sure all lease-loading goroutines are done before returning from restore
* make uniquePoliciesGc discover closed quitCh immediately instead of only when the ticker fires
* make sure all loading goroutines are done before returning from loadEntities, loadCachedEntitiesOfLocalAliases
* Move the ctx capture outside the goroutine to avoid a race
* refactor the toggleable wrapper to avoid races
* Move the capture back outside the goroutine
* defer
* Add a periodic test of the autoseal to detect loss of connectivity
* Keep the logic adjacent to autoseal
* imports
* typo, plus unnecessary constant time compare
* changelog
* pr feedback
* More feedback
* Add locking and a unit test
* unnecessary
* Add timeouts to encrypt/decrypt operations, capture activeContext before starting loop
* Add a block scope for the timeout
* copy/paste ftl
* Refactor to use two timeouts, and cleanup the repetitive failure code
* Readd 0ing gauge
* use millis
* Invert the unit test logic
Seal keys can be rotated. When this happens, the barrier and recovery
keys should be re-encrypted with the new seal key. This change
automatically re-encrypts the barrier and recovery keys with the latest
seal key on the active node during the 'postUnseal' phase.
