Fix FFmpeg 5.x+ compatibility and macOS build issues

[ireneYang]

Description

This PR fixes compilation issues on macOS with newer versions of FFmpeg (5.x+). The changes address API incompatibilities and improve the build process for macOS users.

Changes

1. Fixed av_find_best_stream function call parameter type for FFmpeg 5.x+
2. Updated CMakeLists.txt to disable audio support by default to avoid FFmpeg compatibility issues
3. Added macOS-specific compiler flags for better compatibility
4. Fixed smart pointer definitions in ffmpeg_common.h for newer FFmpeg versions
5. Updated build documentation for macOS users

Testing

• Successfully compiled on macOS with FFmpeg 5.x+
• Verified basic functionality of the library
• Python bindings installed and working correctly

Related Issues

Fixes compilation errors related to:

• av_find_best_stream function signature changes
• AVBSFContextPtr definition issues
• FFmpeg 5.x+ API deprecations

Notes for Reviewers

These changes primarily focus on compatibility with newer FFmpeg versions while maintaining backward compatibility. The audio support is disabled by default to avoid compilation issues, but can be enabled for environments where it works.

[jaminmc]

Try my pull request. It fixes audio, and even adds GPU acceleration to decoding.
#355