[KED-2446] Add new 'sizewarning' flag

[richardwestenra]

Description

1. Add a new 'sizewarning' flag for the large graph warning. This flag is enabled by default, but it's in place so that users can disable it if necessary, if the warning causes them problems. This will also allow us to add a "Don't show this message again" link/button, if we like.
2. Add new tests for the getTriggerLargeGraphWarning selector: Add a test for the flag case, but also add new tests to handle the ignoreLargeWarning and graphHasNodes cases too, which were missed out of [KED-2280] Display size warnings on large graphs #361.
3. Update getTriggerLargeGraphWarning JSDoc comment, to add a bit more detail explaining under what conditions it should return true (i.e. show the warning).

Development notes

For the graphHasNodes test, I needed the state to have a sufficiently large dataset to cross the threshold and trigger the warning, but for the layout to have already been calculated so that the graph object has been updated and populated. In order to achieve this, I prepared the state with a large dataset, then ran it through a reducer with 3 actions: Toggling on a node-type filter to bring it under the threshold, updating the graph state, then toggling the filter back off again to bring the graph back above the threshold.

QA notes

If you set ?sizewarning=0 in the URL with a very large pipeline, the large graph warning shouldn't display.

Checklist

• Read the contributing guidelines
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added new entries to the RELEASE.md file
• Added tests to cover my changes

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[studioswong]

Thanks for setting this PR and adding the tests @richardwestenra, looks great! I just have one confusion about the last test you added in, which I don't think is a scenerio that would exist and having that test in would be rather confusing on the expected behavior for this feature.

Regardless, great stuff!

[studioswong]

Thanks for the clarification - all clear about the test case.

I've left a suggested change for the wording of the test case to make the expected behaviour more apparent.