Remove prefetchBlocksInMem flag along with functionality (#474)

* Remove prefetchBlocksInMem flag

* Remove Indexer method fetchEventsAndSaveBlocks

* Throw error if pruning not safe

---------

Co-authored-by: neeraj <neeraj.rtly@gmail.com>

packages/codegen/src/templates/config-template.handlebars

@@ -87,8 +87,6 @@
   eventsInBatch = 50
   subgraphEventsOrder = true
   blockDelayInMilliSecs = 2000
-  prefetchBlocksInMem = true
-  prefetchBlockCount = 10
 
   # Boolean to switch between modes of processing events when starting the server.
   # Setting to true will fetch filtered events and required blocks in a range of blocks and then process them.

packages/codegen/src/templates/indexer-template.handlebars

@@ -688,10 +688,6 @@ export class Indexer implements IndexerInterface {
     return this._baseIndexer.getBlocksAtHeight(height, isPruned);
   }
 
-  async fetchEventsAndSaveBlocks (blocks: DeepPartial<BlockProgress>[]): Promise<{ blockProgress: BlockProgress, events: DeepPartial<Event>[] }[]> {
-    return this._baseIndexer.fetchEventsAndSaveBlocks(blocks, this.eventSignaturesMap, this.parseEventNameAndArgs.bind(this));
-  }
-
   async fetchAndSaveFilteredEventsAndBlocks (startBlock: number, endBlock: number): Promise<{
     blockProgress: BlockProgress,
     events: DeepPartial<Event>[],