feat: support NO_COLOR (#99) update jenkins slack calls

[qdzlug]

Proposed changes

This change closes #99 by implementing the NO_COLOR variable for our start scripts which will allow the Jenkins output to be a bit cleaner without ANSI color codes.

This also removes the slackSend() calls from the Jenkinsfiles, as this is redundant when the Slack Global plugin is used.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have written my commit messages in the Conventional Commits format.
• I have read the CONTRIBUTING doc
• I have added tests (when possible) that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto master
• I will ensure my PR is targeting the master branch and pulling from my branch from my own fork