Resolve "Graph code coverage changes over time for a project"

What does this MR do?

Implement a new graph that uses echart to render code coverage history under analytic => repository. There was already some work done previously to allow the user to download their code coverage history, but now they can see it live. This graph should show the last 3 months of the history.

During development, I added 2 additional state to the graph:

• an empty graph with an error message if we fail to fetch the data.
• An empty graph with an info message if we get the data, but it's empty

Not that the second state might never happen, but it doesn't hurt to have something ready since we show an empty graph regardless of the data received, it feel safer to include a message for the empty state as well and avoid confusion.

Screenshots

Before

After

Working state

Error State

Empty State

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

There are unit tests written to ensure that the graph renders and can be interacted with. I don't think and E2E test is required since it either show or not the graph and the interaction with the graph should be tested in GitLab-ui