Use filename when printing pending migrations

[adrianna-chang-shopify]

Filename provides the path, whereas basename does not. It makes sense to show the full filename, since migrations can be stored across directories in multi-db apps.

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[swaathi]

This change doesn't show pending migrations across databases though since ActiveRecord::Base.connection.migration_context.open.pending_migrations only counts the pending migrations of the primary database.

[eileencodes]

@swaathi - that's only the case for applications calling check_pending! directly. Internally in Rails we loop through the configs to find the pending migrations and pass those to the pending migrations error. See #46097, #46268, and #46399.

So this change is correct. Now db/animals_migrate/123_some_migration.rb. will be output in the list instead of 123_some_migration.rb.

[eileencodes]

I plan to deprecate check_pending! in favor of calling a method that loops through all the configs, but since it's public I couldn't change it in the previous PRs.