Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
- Test: Fix bucket counting. Previously, the first hit was not counted.
This off-by-one error slightly increased the mean of `*_total_variance`,
which decreased the acceptance rate for a particular random seed
from 95% to 92.6%. (Irrelevant for test failure because the seed is fixed.)
- Improve comments
