Summary:
Bug reported by user: https://gristlabs.getgrist.com/doc/check-ins/p/3#a1.s7.r1183.c19p
Setting x axis to a column of type ChoiceList was breaking chart.
This diff fixes that by splitting the record into several records: one for each choice.
`test/nbrowser/ChartView1.ts` was becoming too big and long to run, so this diff introduces `test/nbrowser/ChartView2.ts` to add more test and `test/nbrowser/chartViewTestUtils.ts` to put all utilities or testing charts.
Test Plan: Adds new test.
Reviewers: georgegevoian
Reviewed By: georgegevoian
Differential Revision: https://phab.getgrist.com/D3041