Move monitoring tests from karma to jest

Problem to solve

As a company, we're investing a lot of our efforts to move from Karma to Jest https://docs.gitlab.com/ee/development/testing_guide/frontend_testing.html#when-should-i-use-jest-over-karma. As a part of that efforts, we should try as much as possible to move existing monitoring related tests from Karma to Jest.

Further details

As of 2019/12/03, we're trying to avoid updating Karma tests unless it is necessary. One such instance was !20208 (comment 254251173).

Below are such tests that need to move to Jest.

1. https://gitlab.com/gitlab-org/gitlab/blob/master/spec/javascripts/monitoring/components/dashboard_spec.js (!21143 (merged))
2. https://gitlab.com/gitlab-org/gitlab/blob/master/spec/javascripts/monitoring/components/graph_group_spec.js (!22039 (merged))
3. https://gitlab.com/gitlab-org/gitlab/blob/master/spec/frontend/monitoring/components/charts/column_spec.js (!21714 (merged))
4. https://gitlab.com/gitlab-org/gitlab/blob/master/spec/frontend/monitoring/components/charts/empty_chart_spec.js (!21714 (merged))
5. https://gitlab.com/gitlab-org/gitlab/blob/master/spec/frontend/monitoring/components/charts/heatmap_spec.js (!21714 (merged))
6. https://gitlab.com/gitlab-org/gitlab/blob/master/spec/frontend/monitoring/components/charts/single_stat_spec.js (!21714 (merged))
7. https://gitlab.com/gitlab-org/gitlab/blob/master/spec/frontend/monitoring/components/charts/time_series_spec.js (!21714 (merged))
8. https://gitlab.com/gitlab-org/gitlab/tree/master/ee/spec/javascripts/monitoring (!22926 (merged))

The only test that will not be migrated will be https://gitlab.com/gitlab-org/gitlab/blob/master/spec/javascripts/monitoring/components/dashboard_resize_spec.js because resize action is specific to a browser and can only be correctly tested through Karma.