Microcopy fix: Rewrite all mandatory field validation error messages to a universal format

**Is your feature request related to a problem? Please describe.**
For mandatory fields, error messages use the label of the field in their text. This makes it harder to keep them correct and updated when changes are done to the labels of the field, also it means more time for translation options.
Example of current behavior:

**Describe the solution you'd like**
All error messages of this type of validation should have an universal format: "This field is mandatory." / "Câmpul este obligatoriu."

**Describe alternatives you've considered**
-

**Additional context**
Changes must be done in the json files, and updates must be noted the Data dictionary