Describe the bug
As an implementer, if I upgrade an old Decidim installation and I didn't execute the command for migrating from legacy decidim-surveys tables to decidim-forms tables, then I lost all my surveys data (!!!).

To Reproduce
Steps to reproduce the behavior:

1. Starting with a legacy installation with data on decidim-surveys tables
2. Execute the upgrade (decidim:upgrade / db:migrate)
3. Go to see the decidim-surveys responses
4. See that I lost my data

Expected behavior
To not have my data removed.
We should be extra careful when remove data and working with legacy tables.
One possible solution would be:

1. Add a migration task that first check if there's content on decidim-surveys legacy tables. This should be executed before removing (of course)
2. On that migration, it should be the code from decidim_surveys:migrate_data_to_decidim_forms task
3. We should also remove the decidim_surveys:migrate_data_to_decidim_forms task as it doesn't make sense now

As an alternative, when executing the migration for deleting the data we should stop and make a warning if there's data on those tables.

Screenshots
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Stacktrace
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Extra data (please complete the following information):

• Decidim Version: 0.23.dev and I'm not so sure if this also is on 0.22 (I didn't check it yet)
• Decidim installation: FundAction

Additional context
This comes from #6178
See comment.