Merge changes Icfc59932,I3d1ca618,Id3966912,I56f74981,Ia9a5dc5e, ... into main

* changes:
  vpx_encoder.h: make flag constants unsigned
  vp8,VP8_COMP: normalize segment_encode_breakout type
  webmdec,WebmInputContext: make timestamp_ns signed
  highbd_quantize_intrin_sse2: quiet int sanitizer warnings
  load_unaligned_u32: use an int w/_mm_cvtsi32_si128
  variance_sse2.c: add some missing casts