feat: Add from-genesis subcommand

[morgsmccauley]

This PR adds the from-genesis subcommand which does the following:

1. Downloads the genesis file from S3 and stores the accounts/access keys defined in it
2. Starts indexing from the genesis block

This does not delete the genesis file after downloading it, this job will be left to the executor.

Majority of this code has been copied from the master-nearcore version of storing genesis records, the obvious difference being that we now need to download the genesis file. I've commented inline where other things differ.

Closes #327

[khorolets]

LGTM overall! I've left a few comments. I don't want to be a blocker here, so I approve it while expecting you to solve my remarks. Thanks!

[khorolets]

@ecp88 I remember we talked about disabling buildkite jobs for all the branches except master-nearcore. Do you have any updates on that?

[khorolets]

Let me know when you finished and I can start a review (disregard my current approval, please)

[kampleforth]

when is this slated to merge? I'm having trouble with the from-block subcommand, it always fails with database query errors

[morgsmccauley]

@kampleforth I am working on this now, you can expect it soon

[khorolets]

when is this slated to merge? I'm having trouble with the from-block subcommand, it always fails with database query errors

There is no guarantee your issue is related to this pull request. Please, consider firing an issue describing the trouble you have with from-block and what exact "database query errors` you struggle with.

We rethought the process

[morgsmccauley]

@khorolets this is ready for re-review now. I've resolved most comments, but left a couple open
because I want to ensure you are onboard with the solutions there :).

[khorolets]

Great job!