Implement Setting Audio Codec Padding

[derrod]

Description

Implements proper setting of the padding present at the start of some audio codec's bitstreams, in OBS that primarily is AAC and Opus.

For more details on priming samples see #10691 and #10689.

Uncompressed or lossless codecs do not require this.

Motivation and Context

Fixes #12949

How Has This Been Tested?

Tested with FFmpeg and CoreAudio AAC.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Tweak (non-breaking change to improve existing functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.