* implement SMTP notifier startup check
* check dial, starttls, auth, mail from, rcpt to, reset, and quit
* log the error on failure
* implement mock
* misc optimizations, adjustments, and refactoring
* implement validate_skip config option
* fix comments to end with period
* fix suites that used smtp notifier without a smtp container
* add docs
* add file notifier startup check
* move file mode into const.go
* disable gosec linting on insecureskipverify since it's intended, warned, and discouraged
* minor PR commentary adjustment
* apply suggestions from code review
Co-Authored-By: Amir Zarrinkafsh <nightah@me.com>
