Add "Validators" field for create validation task flow

[KaterynaKovrizhnykh]

Problem:

When user creates task manually and selects "Is validation task" he is not able to select a validator.

Acceptance Criteria

AC 1: On create task modal there is a "Validators" field instead of  "Annotators" if user selects "Is validation task".
AC 2: The "Validators" drop-down should contain options that were selected during the extraction creation.