[Issue #2471] Update SprintBurndown to use GitHubIssues dataset

[widal001]

Summary

Stacked PR that builds on #2539 to replace the SprintBoard dataset in SprintBurndown and SprintBurnup with the new GitHubIssues dataset.

Fixes #2471

Note: Once we merge in #2539 I'll rebase this branch on main and change the base for the PR to main Rebased ✅

Time to review: 10 mins

Changes proposed

What was added, updated, or removed in this PR.

• Replaces the SprintBoard dataset with GitHubIssues in the SprintBurndown and SprintBurnup metrics
• Reuses intermediate steps to calculate burnup/burndown across both SprintBurnup and SprintBurndown

Context for reviewers

Testing instructions, background context, more in-depth details of the implementation, and anything else you'd like to call out or ask reviewers. Explain how the changes were verified.

1. Follow the instructions to run this code natively (in order to view the chart)
2. Export the data: make delivery-data-export POINTS_FIELD="Story Points"
3. Run burndown: make sprint-burndown

Additional information

Screenshots, GIF demos, code examples or output to help show the changes working as expected.

You should see a chart that looks like this:

And it should output the following stats:

[acouch]

Code LGTM. For clarity, do plan to keep using this once everything is connected with Metabase? Do you plan on using both?

[widal001]

Code LGTM. For clarity, do plan to keep using this once everything is connected with Metabase? Do you plan on using both?

@acouch Great question! @DavidDudas-Intuitial and I were just talking through this yesterday.

I think the tentative plan is to run both in parallel for 2-3 sprints (maybe less) just for quality control then we'll likely deprecate Sprinty McBurndown reports once we can support as is / as was reporting in Metabase.

The base branch was changed.

[widal001]

@DavidDudas-Intuitial I rebased this PR on main so this should be ready for a final review!

@acouch Welcome your review too if you'd like to take another look.

[DavidDudas-Intuitial]

Looks great. Nice work removing the redundant code.