Use region dimensions in SAD and ME

[shssoichiro]

This avoids having to re-check bounds every time we perform SAD, as the region knows its own size. It also may save 2 usize's being passed around during ME. To enforce this, we also remove the w and h parameters from everywhere.

This is part of a series of commits authored by @maj160 to improve performance of rav1e.

[codecov-commenter]

Codecov Report

Base: 86.77% // Head: 86.80% // Increases project coverage by +0.03% 🎉

Coverage data is based on head (c2c7a7a) compared to base (0e2c74c).
Patch coverage: 91.37% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3097      +/-   ##
==========================================
+ Coverage   86.77%   86.80%   +0.03%     
==========================================
  Files          83       83              
  Lines       33105    33098       -7     
==========================================
+ Hits        28727    28732       +5     
+ Misses       4378     4366      -12     

Impacted Files	Coverage Δ
src/api/lookahead.rs	43.34% <0.00%> (+1.13%)	⬆️
src/dist.rs	99.46% <90.00%> (+0.50%)	⬆️
src/me.rs	95.46% <92.20%> (-0.14%)	⬇️
src/api/internal.rs	97.79% <100.00%> (ø)
src/asm/x86/dist/mod.rs	98.87% <100.00%> (+0.01%)	⬆️
src/rdo.rs	85.68% <100.00%> (+0.56%)	⬆️
src/asm/x86/lrf.rs	92.85% <0.00%> (-1.27%)	⬇️
src/asm/x86/predict.rs	43.29% <0.00%> (-0.39%)	⬇️
src/context/mod.rs	92.30% <0.00%> (-0.33%)	⬇️
src/encoder.rs	86.95% <0.00%> (-0.11%)	⬇️
... and 4 more

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[barrbrain]

It seems that some of the assumptions do not hold in certain circumstances. To investigate, I would revert the parts where width and height parameters are removed and assert that they match the region dimensions.

[shssoichiro]

This is going to be rather painful to debug given that it only seems to be failing on x64 Macos. Why that is, I have no clue... I'll fix it up when I have a moment.