Fix Bitrate Update for Video Streaming

[t-yoshii]

Fixes #1392

This PR is ready for review.

Risk

This PR makes no API changes.

Testing Plan

I tested with our internal devboard.

Summary

reflect bitrate value returned from HMI in video encoder settings, except the case that app specified custom bitrate in encoder settings.

Changelog

Enhancements

• reflect bitrate value returned from HMI in video encoder settings, except the case that app specified custom bitrate in encoder settings.

CLA

• I have signed the CLA

[t-yoshii]

Hello @NicoleYarroch @joeljfischer ,

#1392 is resolved by #1393, however, we have reconsidered how to fix #1392

Fix #1393 has 2 problems.

1. By default, customVideoSettings is overwritten by HMI capabilities. This breaks current SDL app behavior which uses customeVideoSettings.
2. The flag allowOverrideEncoderSettings is a little bit confusing.

So, we applied a new fix with following rules.
a. customVideoEncoderSettings is always applied. i.e. customVideoEncoderSettings > HMI capabilities > defaultVideoEncoderSettings.
b. Do not introduce additional flag (such as allowOverrideEncoderSettings) for simplicity.

Since customVideoSettings is the value that is explicitly set by the application, it should always have the highest priority (than HMI's value).

Could you please kindly review this again? I am sorry for requesting review twice. Thank you.