DB Index is created over ergoTreeTemplate which is being created for all ergoTrees instead of just P2PK

Hi,

This might improve performance a lot in both query time and indexing time.

Problem :
- ErgoTreeTemplate is created here for ALL ErgoTrees instead of just P2SH. The Template is always the same for P2PK which creates a SuperNode containing extreme amount of boxes https://github.com/ergoplatform/explorer-backend/blob/master/modules/chain-grabber/src/main/scala/org/ergoplatform/explorer/indexer/extractors/package.scala#L139
- creating db Index over this column with supernodes is quite inefficient https://github.com/ergoplatform/explorer-backend/blob/master/modules/explorer-core/src/main/resources/db/V9__Schema.sql#L153