Log Message:
svt-av1: update to 1.8.0.

## [1.8.0] - 2023-12-11

Encoder
- Improve the tradeoffs for the random access mode across presets:
- Speedup CRF presets M6 to M0 by 17-53% while maintaining similar quality levels
- Re-adjust CRF presets M7 to M13 for better quality with BD-rate gains ranging \ 
from 1-4%
- Improve the quality and speed of the 1-pass VBR mode
- More details on the per preset improvements can be found in MR !2143
- Add API allowing to update bitrate / CRF and Key_frame placement during the \ 
encoding session for CBR lowdelay mode and CRF Random Access mode
- ARM Neon SIMD optimizations for most critical kernels allowing for a 4.5-8x \ 
fps speedup vs the c implementation

Cleanup and bug fixes and documentation
- Various cleanups and functional bug fixes
- Update the documentation for preset options and individual features