archive node consumes a lot of memory with --config-file flag

[ghost-not-in-the-shell]

When start an archive node the first time with --config-file flag, it would try to add the genesis accounts, and this would consumes a lot of memory. For example, in short-epoch dry run network, the memory usage of the archive node takes about 50 GB of memory and the initialization process takes about an hour.

This --config-file flag is optional. In theory, it's not needed for migrated database, because accounts in the fork genesis ledger has already been populated by migration.

Suggestion: we should add this to the doc, so that user would not be surprised by the high memory usage.