style: use builtin 'command -v' instead of nonstandard 'which'

[mboersma]

Reason for Change:
Enforces the use of POSIX shell builtin command -v instead of the nonstandard which command.

See https://github.com/koalaman/shellcheck/wiki/SC2230

Issue Fixed:

Refs #953

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[codecov]

Codecov Report

Merging #1185 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1185   +/-   ##
=======================================
  Coverage   74.66%   74.66%           
=======================================
  Files         128      128           
  Lines       18210    18210           
=======================================
  Hits        13597    13597           
  Misses       3829     3829           
  Partials      784      784

[jackfrancis]

/lgtm

[acs-bot]

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