config: backport the rename of fastsync to blocksync (#9259)

This is largely a cherry pick of #6755 with some additional fixups added where detected. 
This change moves the blockchain package to a package called blocksync. Additionally, it renames the relevant uses of the term `fastsync` to `blocksync`.

closes: #9227 

#### PR checklist

- [ ] Tests written/updated, or no tests needed
- [x] `CHANGELOG_PENDING.md` updated, or no changelog entry needed
- [x] Updated relevant documentation (`docs/`) and code comments, or no
      documentation updates needed

test/e2e/generator/generate.go

@@ -28,7 +28,7 @@ var (
 	// FIXME: grpc disabled due to https://github.com/tendermint/tendermint/issues/5439
 	nodeABCIProtocols     = uniformChoice{"unix", "tcp", "builtin"} // "grpc"
 	nodePrivvalProtocols  = uniformChoice{"file", "unix", "tcp"}
-	nodeFastSyncs         = uniformChoice{false, true}
+	nodeBlockSyncs        = uniformChoice{"v0"} // "v2"
 	nodeStateSyncs        = uniformChoice{false, true}
 	nodeMempools          = uniformChoice{"v0", "v1"}
 	nodePersistIntervals  = uniformChoice{0, 1, 5}
@@ -201,7 +201,7 @@ func generateNode(
 		StartAt:          startAt,
 		Database:         nodeDatabases.Choose(r).(string),
 		PrivvalProtocol:  nodePrivvalProtocols.Choose(r).(string),
-		FastSync:         nodeFastSyncs.Choose(r).(bool),
+		BlockSync:        nodeBlockSyncs.Choose(r).(string),
 		Mempool:          nodeMempools.Choose(r).(string),
 		StateSync:        nodeStateSyncs.Choose(r).(bool) && startAt > 0,
 		PersistInterval:  ptrUint64(uint64(nodePersistIntervals.Choose(r).(int))),