control video quality as "Average Bitrate (kbps)" instead of arbitrary Number

[StoopidoMan]

Is your feature request related to a problem? Please describe.
I understand bitrate better it is consistent number

Describe the solution you'd like
In Handbrake I can choose either quality or average bitrate which later is easier for me to understand than just an arbitrary number.

In the screenshot below it shows how you can switch between the two modes in handbrake:

However, I don't like Handbrake UI and user experience it is not intuitive, the UI should look simple so it would be easy for most users, thus I suggest a drop down style switch instead of graying out the unselected mode.

Meaning First you replace "Quality" with "Quality Mode"

And beside "Quality Mode" you have a a drop down button titled "integer"

and when you click on it, you will have two option "integer" and "Average Bitrate"

when you choose one of these average bit rate, below it or beside it, the quality bar will change to a text box

This will make the UI look less cluttered and less option visible to new users

Describe alternatives you've considered
When you click advance it shows the command line thing, but also some advance option like average bitrate instead of the quality bar and when average bitrate is set, it automatically will add that code to the "Custom arguments" field most advanced users prefer to do things on a gui, we are not Advanced advanced users. just advanced

Additional context
#386 (comment)