Fills datasets that do not have all the datapoints with 0 so that every
line in the graph starts at the beginning and ends at the end of graph.
Closes #
[1-2256](https://linear.app/unleash/issue/1-2256/fill-the-data-with-0s-so-that-all-x-axis-labels-have-values)
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Signed-off-by: andreas-unleash <andreas@getunleash.ai>
Co-authored-by: Tymoteusz Czech <2625371+Tymek@users.noreply.github.com>