Create a dynamic form for basic addition of grade item in Gradebook setup

Summary:

This issue is a part of the proposed improvements to the simplified addition of items in the Gradebook setup.

Figma link

Since the simplified (basic) addition of grade items in the Gradebook setup will be done using modal forms, the aim of this issue is to set the initial backend infrastructure by creating the required dynamic form.

Scope:

1. Create a class that extends core_form\dynamic_form.
2. The dynamic form contains all form elements as specified in the figma prototype
3. The dynamic form should accept an optional parameter - category ID, to determine whether the category select form element should be present or not (depending whether the form is triggered through a specific grade category or through the tertiary navigation)