Prune TBAR stores that hold intermediate date

[meiersi-da]

That is the tables backing these two stores:

• splice/apps/scan/src/main/scala/org/lfdecentralizedtrust/splice/scan/store/ScanAppRewardsStore.scala

  Line 15 in d5d1108

  trait ScanAppRewardsStore {

• splice/apps/scan/src/main/scala/org/lfdecentralizedtrust/splice/scan/store/ScanRewardsReferenceStore.scala

  Line 31 in d5d1108

  trait ScanRewardsReferenceStore extends AppStore {

The goal is that the performance of the reward computation is independent of the time it has been running.

Note that the pruning of the AppActivityStore will be done separately, as part of the work be the Splice Maintainers to store the verdicts in a bulk format outside of the Scan DB.