Campaign dates as dataset attribute + fix user locale settings

[tokland]

:pushpin: References

• Issue: Closes https://app.clickup.com/t/8693twdvt

:memo: Implementation

• We now use an attribute (for data sets) containing a JSON string. Metadata: metadata-data-input-periods.json
• When a campaign is loaded, it gets the period from the new attribute or, if empty (existing campaigns), from dataInputPeriods. On campaign save, the attribute is always set, and DIP is emptied.
• The old code used dhis2.de.storageManager.getUserSettings() (form.js), but this function, at least in 2.37, only returns key keyAnalysisDisplayProperty (we need keyDbLocale). Refactor: get user settings with a call.

:fire: Reviewer

• This PR includes a refactor of localization of the data entry, so it should be tested. Save the campaign with a certain locale, change the user DB locale to another, reload data entry, the new locale should be shown.