[cleanup] Use FFmpeg for AV_RBxx, AV_WBxx and AV_WLxx functions and drop 'BitstreamWriter.cpp'

[thexai]

Description

• Use FFmpeg for AV_RBxx, AV_WBxx and AV_WLxx functions
• Drop utils/BitstreamWriter.cpp

Motivation and context

With #25172 I realized that we are using a replica of FFmpeg AV_RB24, AV_RB32, etc.. functions when the FFmpeg header is available currently <libavutil/intreadwrite.h> and in fact is already used in some places:

xbmc/xbmc/cores/AudioEngine/Utils/PackerMAT.cpp

Line 80 in adad147

const uint16_t frameTime = AV_RB16(data + 2);

Then is a direct replacement to remove duplicated code.

Once replaced also utils/BitstreamWriter.cpp is a dead code because CBitstreamWriter::WriteBits() it's not used in any place.

How has this been tested?

Runtime tested in Shield with Dolby Vision profile 7 file that make use of BitstreamConverter when enabled DV compatibility mode (profile 7 ---> 8 conversion).

What is the effect on users?

nothing

Screenshots (if appropriate):

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• Student submission (PR was done for educational purposes and will be treated as such)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed