Merge branch 'mr/bisect-in-c-4'

Merge branch 'mr/bisect-in-c-4'

Rewrite of "git bisect" in C continues.

* mr/bisect-in-c-4:
  bisect--helper: retire `--bisect-next-check` subcommand
  bisect--helper: reimplement `bisect_run` shell function in C
  bisect--helper: reimplement `bisect_visualize()` shell function in C
  run-command: make `exists_in_PATH()` non-static
  t6030-bisect-porcelain: add test for bisect visualize
  t6030-bisect-porcelain: add tests to control bisect run exit cases