Process forms in chunks or use pagination

[susnux]

This is more of a meta issue.

Currently for a lot of operations we query all (forms, submissions...) but for large instances this might get a problem if there are e.g. 30'000 forms or 3'000 submissions.

We should figure out a good way to handle:

• #2030
• Show form results (fetching the results might be bad if there are hundreds or thousands of submissions)
• Investigate if there are more places that are problematic

[Chartman123]

findAll() in FormsMapper is only used for shared forms. So I think that we could already filter the following forms:

• showToAllUsers in access_json is true in forms table
• rows in shares table for form_id and share_with = current user