Skip form's default hidden fields to be stored in the configuration

Problem/Motivation

I noticed that when the configuration of the module is saved, Some extra values are also saved in the configuration with a null value.
It is because in the configuration form submit handler, Values are saved using the loop. So the default hidden fields will also be saved.
For example

twilio_callback_container: null
actions: null
form_build_id: form-G-EIQPFWO2eYjLMyCWm6skwLrAidpeY7Pq_dK2Urq1c
form_token: BgIbQIiy3scVJdcwHkwDpVxtJsOYDrIY0cR1XyNoThU
form_id: twilio_admin_form

Steps to reproduce

Proposed resolution

Skip unnecessary fields to be saved in the configuration.

Remaining tasks

User interface changes

API changes

Data model changes