Merge branch 'use-activerecord_sane_schema_dumper' into 'master'

Use activerecord_sane_schema_dumper

## What does this MR do?

> `ActiveRecord::SaneSchemaDumper` modifies the behavior of Rails’ `ActiveRecord::SchemaDumper` so that the generated `db/schema.rb` file doesn’t contain any useless/harmful whitespace column alignment.

## Why was this MR needed?

To reduce potential conflicts in `db/schema.rb` (see https://gitlab.com/gitlab-org/gitlab-ee/issues/715).

See merge request !6827