tests: output --version of program under test

tests: output --version of program under test

This touches all new tests added since commit b062bbd9, when
init.cfg was added.  Older tests still exist that could use
conversion, but we can address those later.

* tests/sample-test: Restore hint for --version output.
* tests/misc/stat-birthtime: Include --version if verbose.
* tests/misc/tr-case-class: Likewise.
* tests/misc/stat-mount: Likewise.
* tests/misc/sort-unique: Likewise.
* tests/misc/sort-benchmark-random: Likewise.
Suggested by Jim Meyering.