services/horizon: require COUNT param for horizon db migrate commands

[paulbellamy]

Fixes #3720

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with name of package that is most changed in the PR, ex.
  services/friendbot, or all or doc if the changes are broad or impact many
  packages.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.
• I've updated any docs (developer docs, .md
  files, etc... affected by this change). Take a look in the docs folder for a given service,
  like this one.

Release planning

• I've updated the relevant CHANGELOG (here for Horizon) if
  needed with deprecations, added features, breaking changes, and DB schema changes.
• I've decided if this PR requires a new major/minor version according to
  semver, or if it's mainly a patch change. The PR is targeted at the next
  release branch if it's not a patch change.

What

Require the COUNT param for horizon db migrate down COUNT (and redo, to prevent accidentally running all downward migrations. up is unchanged, so you can run all upwards migrations.

Add a horizon db migrate status command, printing migrations and the time they were applied. A short-term fix to make figuring out the count possible. Output like:

$ horizon db migrate status
Migration                                                       Applied
1_initial_schema.sql                                            2021-06-29 16:29:19.728113 +0000 UTC
2_index_participants_by_toid.sql                                2021-06-29 16:29:19.729313 +0000 UTC
3_use_sequence_in_history_accounts.sql                          2021-06-29 16:29:19.730471 +0000 UTC
4_add_protocol_version.sql                                      2021-06-29 16:29:19.731004 +0000 UTC
5_create_trades_table.sql                                       2021-06-29 16:29:19.732911 +0000 UTC
6_create_assets_table.sql                                       2021-06-29 16:29:19.734534 +0000 UTC
7_modify_trades_table.sql                                       2021-06-29 16:29:19.737889 +0000 UTC
8_add_aggregators.sql                                           2021-06-29 16:29:19.739113 +0000 UTC
...

Why

It's a bit of a footgun at the moment. The default behaviour of horizon db migrate down is maximum destruction.

Known limitations

• Figure out where to document this. (especially using status to figure out how many steps to migrate down). Suggestions welcome...

[2opremio]

I think that for the migrate status command it would be really useful for each row to also print what migrate down/up COUNT command is needed to get there. I can create a separate ticket for that if you prefer.

[2opremio]

Optionally, it would be useful to have a integration test for the migration commands.

[paulbellamy]

Opened #3744 to track any improvements to horizon db migrate status