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

❌ Patch coverage is 91.37931% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.80%. Comparing base (c2dfb35) to head (bc171d7).
⚠️ Report is 409 commits behind head on master.

Files with missing lines	Patch %	Lines
src/me.rs	92.20%	6 Missing ⚠️
src/api/lookahead.rs	0.00%	3 Missing ⚠️
src/dist.rs	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3097      +/-   ##
==========================================
- Coverage   86.81%   86.80%   -0.02%     
==========================================
  Files          83       83              
  Lines       33104    33101       -3     
==========================================
- Hits        28740    28734       -6     
- Misses       4364     4367       +3     

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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.