adding average nodes visited to benchmark tests

[MarkWolters]

This PR is to add the value of average nodes visited to the metrics tested by the regression tests defined in AutoBenchYAML, which are used by the automated regression testing GitHub action.

Includes changes to the post-hoc script for visualization of regression test results.

[github-actions]

Before you submit for review:

• Does your PR follow guidelines from CONTRIBUTIONS.md?
• Did you summarize what this PR does clearly and concisely?
• Did you include performance data for changes which may be performance impacting?
• Did you include useful docs for any user-facing changes or features?
• Did you include useful javadocs for developer oriented changes, explaining new concepts or key changes?
• Did you trigger and review regression testing results against the base branch via Run Bench Main?
• Did you adhere to the code formatting guidelines (TBD)
• Did you group your changes for easy review, providing meaningful descriptions for each commit?
• Did you ensure that all files contain the correct copyright header?

If you did not complete any of these, then please explain below.

[marianotepper]

LGTM

[jshook]

Looks good to me