core, cmd/geth: add --override.* flags to geth init (#28407)

* core, cmd/geth: add --override.* flags to geth init

* also apply overrides before genesis commit with new block

* review feedback

core/genesis.go

@@ -287,11 +287,11 @@ func SetupGenesisBlockWithOverride(db ethdb.Database, triedb *trie.Database, gen
 		} else {
 			log.Info("Writing custom genesis block")
 		}
+		applyOverrides(genesis.Config)
 		block, err := genesis.Commit(db, triedb)
 		if err != nil {
 			return genesis.Config, common.Hash{}, err
 		}
-		applyOverrides(genesis.Config)
 		return genesis.Config, block.Hash(), nil
 	}
 	// The genesis block is present(perhaps in ancient database) while the
@@ -303,6 +303,7 @@ func SetupGenesisBlockWithOverride(db ethdb.Database, triedb *trie.Database, gen
 		if genesis == nil {
 			genesis = DefaultGenesisBlock()
 		}
+		applyOverrides(genesis.Config)
 		// Ensure the stored genesis matches with the given one.
 		hash := genesis.ToBlock().Hash()
 		if hash != stored {
@@ -312,11 +313,11 @@ func SetupGenesisBlockWithOverride(db ethdb.Database, triedb *trie.Database, gen
 		if err != nil {
 			return genesis.Config, hash, err
 		}
-		applyOverrides(genesis.Config)
 		return genesis.Config, block.Hash(), nil
 	}
 	// Check whether the genesis block is already written.
 	if genesis != nil {
+		applyOverrides(genesis.Config)
 		hash := genesis.ToBlock().Hash()
 		if hash != stored {
 			return genesis.Config, hash, &GenesisMismatchError{stored, hash}