Add a routine to purge state tombstones

[imsdu]

Describe the bug
State tombstones allows for indexing to delete resources from a view if their type changed and did not fit the type restriction on the view anymore.

This table is meant to be purged after the tombstone reaches a given ttl.
The routine responsible for purging the tombstone is missing and needs to be implemented as the table is growing and the indexing query is getting slower where

Expected behavior

• Tombstones should be purged when they reached the ttl

This should be handled in the same way as how we purge views restart requests for example