core, core/rawdb, eth/sync: no tx indexing during snap sync (#28703)

This change simplifies the logic for indexing transactions and enhances the UX when transaction is not found by returning more information to users.

Transaction indexing is now considered as a part of the initial sync, and `eth.syncing` will thus be `true` if transaction indexing is not yet finished. API consumers can use the syncing status to determine if the node is ready to serve users.

interfaces.go

@@ -120,6 +120,18 @@ type SyncProgress struct {
 
 	HealingTrienodes uint64 // Number of state trie nodes pending
 	HealingBytecode  uint64 // Number of bytecodes pending
+
+	// "transaction indexing" fields
+	TxIndexFinishedBlocks  uint64 // Number of blocks whose transactions are already indexed
+	TxIndexRemainingBlocks uint64 // Number of blocks whose transactions are not indexed yet
+}
+
+// Done returns the indicator if the initial sync is finished or not.
+func (prog SyncProgress) Done() bool {
+	if prog.CurrentBlock < prog.HighestBlock {
+		return false
+	}
+	return prog.TxIndexRemainingBlocks == 0
 }
 
 // ChainSyncReader wraps access to the node's current sync status. If there's no