Create reusable tooltip for bar chart

[HenrikeW]

Related issue(s) and PR(s)

This PR closes #592.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

List of changes made

• a reusable Tooltip component was created, based on what was already used on the favorite rows
• the tooltip on the favorite rows was replaced by the new component
• the new component was used to show a tooltip on all sections of the bar chart
• the styling of the bar chart had to be slightly adjusted to make the tooltip work (replacing overflow: hidden with another border radius)

Screenshot of the fix

Testing

• go to the report page and hover over the sections of the bar chart. You should see the tooltip appearing above
• also try to hover over the favorite rows. You should see the same tooltip as before

Further comments

Definition of Done checklist

• I have made an effort making the commit history understandable
• I have performed a self-review of my own code and commented any hard-to-understand areas
• Tests and lint/format validations are passing
• My changes generate no new warnings

[ghost]

Code-review only. Looks good. Good idea to create a re-usable component.

[KattisLej]

Works as expected both on favorites and on the bar chart.