Use branchless binary search to find_min_version

[pickfire]

Constant search time and no unpredictable conditional branches
Benchmark results: 39 ns/iter -> 2 ns/iter (including multiple call)

Based on rust-lang/rust#45333
Inspired by https://raw.githubusercontent.com/RustStudy/rust_daily_news/master/img/%E4%BA%8C%E7%BB%B4%E7%A0%81%E7%94%9F%E6%88%90.png

[coveralls]

Coverage increased (+0.007%) to 93.5% when pulling 81404ac on pickfire:branchless into a585403 on kennytm:master.

[kennytm]

Thanks!