While running a command from the integration tests, invoke `.result` to
trigger a save of the result set, but don't call `.format!` to avoid
(re)generating the HTML output with every run. The final output will
still be written once the main unit test run completes.
This significantly speeds up the integration tests, that take about 1/3
less time to complete when not generating the intermediate output.
ClosesHomebrew/homebrew#48280.
Signed-off-by: Martin Afanasjew <martin@afanasjew.de>