Improve Slack Notification Step For Adhoc

[stanbrub]

As of now, there is a slack notification step in the remote-benchmark.yml workflow. Some categories like nightly use it to publish tables to slack at the end of a run. Others like adhoc disable it by supplying no slack token in the scale-benchmark.properties file.

Notes:

• The slack notification step is not used for adhoc runs
• Deephaven is installed and started whether or not the publish actually uses it

Improvements:

• Cancel the slack publish step entirely if a category doesn't use it
• Only install Deephaven if the specific publish uses it
  • For example, 2 categories may publish to slack but only one needs Deephaven